| transcription and sequence studies of a 4.3-kbp fragment from a ds-dna eukaryotic algal virus. | a 4.3-kbp portion of the genome from the chlorella virus, pbcv-1, has been cloned and sequenced. minimally, five open reading frames (orfs) were identified on this fragment. transcriptional analysis indicates that each orf encodes complex patterns of rna. the total length of transcribed rna exceeds that of the orf indicating either post-transcriptional modification or multiple transcriptional start/stop sites. the sequence tttttnt, previously described as the transcriptional stop site for the ea ... | 1990 | 2345963 |
| characterization of a protein kinase gene from two chlorella viruses. | an open reading frame (orf) with strong homology to eukaryotic serine/threonine protein kinases was found in the two chlorella viruses sc-1a and pbcv-1. the deduced molecular weights of each putative protein kinase were 35 kda and the predicted amino acid sequences of the two proteins were 95% identical. the orf encoding the sc-1a protein kinase was over-expressed as a fusion protein in escherichia coli. the recombinant fusion protein had autophosphorylation activity and could phosphorylate cert ... | 1995 | 7785317 |
| identification and molecular cloning of a unique hyaluronan synthase from pasteurella multocida. | type a pasteurella multocida, a prevalent animal pathogen, employs a hyaluronan [ha] polysaccharide capsule to avoid host defenses. we utilized transposon insertional mutagenesis to identify the p. multocida ha synthase, the enzyme that polymerizes ha. a dna fragment from a wild-type genomic library could direct ha production in vivo in escherichia coli, a bacterium that normally does not produce ha. analysis of truncated plasmids derived from the original clone indicated that an open reading fr ... | 1998 | 9525958 |
| characterization of a novel cis-syn and trans-syn-ii pyrimidine dimer glycosylase/ap lyase from a eukaryotic algal virus, paramecium bursaria chlorella virus-1. | endonuclease v from bacteriophage t4, is a cis-syn pyrimidine dimer-specific glycosylase. recently, the first sequence homolog of t4 endonuclease v was identified from chlorella virus paramecium bursaria chlorella virus-1 (pbcv-1). here we present the biochemical characterization of the chlorella virus pyrimidine dimer glycosylase, cv-pdg. interestingly, cv-pdg is specific not only for the cis-syn cyclobutane pyrimidine dimer, but also for the trans-syn-ii isomer. this is the first trans-syn-ii- ... | 1998 | 9582353 |
| a potassium channel protein encoded by chlorella virus pbcv-1. | the large chlorella virus pbcv-1, which contains double-stranded dna (dsdna), encodes a 94-codon open reading frame (orf) that contains a motif resembling the signature sequence of the pore domain of potassium channel proteins. phylogenetic analyses of the encoded protein, kcv, indicate a previously unidentified type of potassium channel. the messenger rna encoded by the orf leads to functional expression of a potassium-selective conductance in xenopus laevis oocytes. the channel blockers amanta ... | 2000 | 10698737 |
| hyaluronan synthase of chlorella virus pbcv-1. | sequence analysis of the 330-kilobase genome of the virus pbcv-1 that infects a chlorella-like green algae revealed an open reading frame, a98r, with similarity to several hyaluronan synthases. hyaluronan is an essential polysaccharide found in higher animals as well as in a few pathogenic bacteria. expression of the a98r gene product in escherichia coli indicated that the recombinant protein is an authentic hyaluronan synthase. a98r is expressed early in pbcv-1 infection and hyaluronan is produ ... | 1997 | 9388183 |
| analysis of 74 kb of dna located at the right end of the 330-kb chlorella virus pbcv-1 genome. | this report completes a preliminary analysis of the sequence of the 330,740-bp chlorella virus pbcv-1 genome, the largest virus genome to be sequenced to date. the pbcv-1 genome is 57% the size of the genome from the smallest self-replicating organism, mycoplasma genitalium. analysis of 74 kb of newly sequenced dna, from the right terminus of the pbcv-1 genome, revealed 153 open reading frames (orfs) of 65 codons or longer. eighty-five of these orfs, which are evenly distributed on both strands ... | 1997 | 9356347 |
| chlorella virus sc-1a encodes at least five functional and one nonfunctional dna methyltransferases. | chlorella virus sc-1a encodes at least six dna methyltransferases (mtases): four n6-methyldeoxyadenine (m6a) mtases, m x cvisi (tgcma), m x cvisii (cmatg), m x cvisiii (tcgma) and m x cvisiv (gmatc), one 5-methyldeoxycytosine (m5c) mtase, m x cvisv (approximately rcmcg), and one nonfunctional m5c mtase, m x cvisvi, which is homologous to the mtase m x cviji [rgmc(t/c/g)] produced by another chlorella virus il-3a. genes encoding three of the sc-1a m6a mtases (m x cvisi, m x cvisii, and m x cvisii ... | 1997 | 9197539 |
| chlorella virus pbcv-1 encodes a homolog of the bacteriophage t4 uv damage repair gene denv. | the bacteriophage t4 denv gene encodes a well-characterized dna repair enzyme involved in pyrimidine photodimer excision. we have discovered the first homologs of the denv gene in chlorella viruses, which are common in fresh water. this gene functions in vivo and also when cloned in escherichia coli. photodamaged virus dna can also be photoreactivated by the host chlorella. since the chlorella viruses are continually exposed to solar radiation in their native environments, two separate dna repai ... | 1997 | 9097450 |
| characterization of an atp-dependent dna ligase encoded by chlorella virus pbcv-1. | we report that chlorella virus pbcv-1 encodes a 298-amino-acid atp-dependent dna ligase. the pbcv-1 enzyme is the smallest member of the covalent nucleotidyl transferase superfamily, which includes the atp-dependent polynucleotide ligases and the gtp-dependent rna capping enzymes. the specificity of pbcv-1 dna ligase was investigated by using purified recombinant protein. the enzyme catalyzed efficient strand joining on a singly nicked dna in the presence of magnesium and atp (km, 75 microm). ot ... | 1997 | 9032324 |
| analysis of 76 kb of the chlorella virus pbcv-1 330-kb genome: map positions 182 to 258. | analysis of 76 kb of newly sequenced dna, located between map positions 182 and 258 kb in the 330-kb chlorella virus pbcv-1 genome, revealed 175 open reading frames (orfs) of 65 codons or longer. one hundred and five of these 175 orfs were considered major orfs. twenty-one of the 105 major orfs resembled proteins in databases including ribonucleotide reductase small subunit, rnase iii, thioredoxin, glutaredoxin, protein disulfide isomerase, deoxynucleoside kinase, frog virus 3 atpase, acetobacte ... | 1996 | 8806566 |
| expression and characterization of an rna capping enzyme encoded by chlorella virus pbcv-1. | we report that the a103r protein of chlorella virus pbcv-1 is an mrna capping enzyme that catalyzes the transfer of gmp from gtp to the 5' diphosphate end of rna. this is a two-step reaction in which the enzyme first condenses with gtp to form a covalent enzyme-gmp intermediate and then transfers the gmp to an rna acceptor to form a gpppn cap. purified recombinant al03r is a 38-kda monomer that lacks rna (guanine-7-) methyltransferase activity. with respect to its size, amino acid sequence, and ... | 1996 | 8794301 |
| analysis of 94 kb of the chlorella virus pbcv-1 330-kb genome: map positions 88 to 182. | analysis of 94 kb of dna, located between map positions 88 and 182 kb in the 330-kb chlorella virus pbcv-1 genome, revealed 195 open reading frames (orfs) 65 codons or longer. one hundred and five of the 195 orfs were considered major orfs. twenty-six of the 105 major orfs resembled genes in the databases including three chitinases, a chitosanase, three serine/threonine protein kinases, two additional protein kinases, a tyrosine protein phosphatase, two ankyrins, an ornithine decarboxylase, a co ... | 1996 | 8614977 |
| paramecium bursaria chlorella virus-1 encodes an unusual arginine decarboxylase that is a close homolog of eukaryotic ornithine decarboxylases. | paramecium bursaria chlorella virus (pbcv-1) is a large double-stranded dna virus that infects chlorella-like green algae. the virus encodes a homolog of eukaryotic ornithine decarboxylase (odc) that was previously demonstrated to be capable of decarboxylating l-ornithine. however, the active site of this enzyme contains a key amino acid substitution (glu for asp) of a residue that interacts with the delta-amino group of ornithine analogs in the x-ray structures of odc. to determine whether this ... | 2004 | 15190062 |
| analysis of 45 kb of dna located at the left end of the chlorella virus pbcv-1 genome. | forty-five kilobases of dna, including the previously sequenced 2.2-kb inverted repeat region, located at the left termini of the 330-kb chlorella virus pbcv-1 genome were sequenced and analyzed. eighty-five complete open reading frames (orfs) larger than 195 nucleotides were identified. thirty-seven of the 85 orfs, which are densely packed on both strands of the dna, were considered major orfs. fifteen of the major orfs have similarity to genes in the databases, including bacterial glycerophosp ... | 1995 | 7831789 |
| amplification of dna polymerase gene fragments from viruses infecting microalgae. | nested pcr with three highly degenerate primers was used for amplification and identification of dna polymerase (pol) genes from viruses which infect three genera of microalgae. group-specific primers (avs1 and avs2) were designed on the basis of inferred amino acid sequences unique to the dna pol genes of viruses (pbcv-1 and ny-2a) that infect an endosymbiotic chlorella-like alga (chlorophyceae) and a virus (mpv-sp1) which infects the photosynthetic flagellate micromonas pusilla (prasinophyceae ... | 1995 | 7747950 |
| dna methyltransferase induced by pbcv-1 virus infection of a chlorella-like green alga. | a dna methyltransferase was isolated from a eucaryotic, chlorella-like green alga infected with the virus pbcv-1. the enzyme recognized the sequence gatc and methylated deoxyadenosine solely in gatc sequences. host dna, which contains gatc sequences, but not pbcv-1 dna, which contains gmatc sequences, was a good substrate for the enzyme in vitro. the dna methyltransferase activity was first detected about 1 h after viral infection; pbcv-1 dna synthesis and host dna degradation also began at abou ... | 1986 | 3537703 |
| chlorella virus-encoded deoxyuridine triphosphatases exhibit different temperature optima. | a putative deoxyuridine triphosphatase (dutpase) gene from chlorella virus pbcv-1 was cloned, and the recombinant protein was expressed in escherichia coli. the recombinant protein has dutpase activity and requires mg(2+) for optimal activity, while it retains some activity in the presence of other divalent cations. kinetic studies of the enzyme revealed a k(m) of 11.7 microm, a turnover k(cat) of 6.8 s(-1), and a catalytic efficiency of k(cat)/k(m) = 5.8 x 10(5) m(-1) s(-1). dutpase genes were ... | 2005 | 16014955 |
| the termini of the chlorella virus pbcv-1 genome are identical 2.2-kbp inverted repeats. | the chlorella virus pbcv-1 genome is a linear nonpermuted 333-kbp dsdna molecule with covalently closed hairpin termini. the termini (minus the hairpin) are identical inverted repeats of at least 2185 bases after which the sequence diverges. the inverted repeats contain two small potential open reading frames and several direct repeats. however, neither the open reading frames nor the remainder of the inverted repeats are transcribed during pbcv-1 replication. twenty-nine other chlorella virus d ... | 1991 | 1989390 |
| a single amino acid change restores dna cytosine methyltransferase activity in a cloned chlorella virus pseudogene. | the chlorella virus pbcv-1 contains an open reading frame, named p17-orf4, which differs by eight amino acids from a dna cytosine methyltransferase, m.cviji, encoded by a different chlorella virus il-3a. whereas il-3a expresses m.cviji, which methylates the central cytosine in (a/g)gc(t/c/g) sequences, p17-orf4 is non-functional. gene fusions between p17-orf4 and m.cviji and site-directed point mutations revealed that changing gln188 to lys188 abolishes m.cviji methyltransferase activity. conver ... | 1992 | 1579454 |
| characterization of chlorella virus pbcv-1 cviaii restriction and modification system. | a second dna site-specific (restriction) endonuclease (r.cviaii) and its cognate adenine dna methyltransferase (m.cviaii) were isolated from virus pbcv-1 infected chlorella strain nc64a cells. r.cviaii, a heteroschizomer of the bacterial restriction endonuclease nlaiii, recognizes the sequence catg, and does not cleave cmatg sequences. however, unlike nlaiii, which cleaves after the g and does not cleave either cmatg or mcatg sequences, cviaii cleaves between the c and a and is unaffected by mca ... | 1992 | 1437552 |
| topoisomerase ii from chlorella virus pbcv-1 has an exceptionally high dna cleavage activity. | chlorella virus pbcv-1 topoisomerase ii is the only functional type ii enzyme known to be encoded by a virus that infects eukaryotic cells. however, it has not been established whether the protein is expressed following viral infection or whether the enzyme has any catalytic features that distinguish it from cellular type ii topoisomerases. therefore, the present study characterized the physiological expression of pbcv-1 topoisomerase ii and individual reaction steps catalyzed by the enzyme. res ... | 2001 | 11323425 |
| rna triphosphatase component of the mrna capping apparatus of paramecium bursaria chlorella virus 1. | paramecium bursaria chlorella virus 1 (pbcv-1) elicits a lytic infection of its unicellular green alga host. the 330-kbp viral genome has been sequenced, yet little is known about how viral mrnas are synthesized and processed. pbcv-1 encodes its own mrna guanylyltransferase, which catalyzes the addition of gmp to the 5' diphosphate end of rna to form a gpppn cap structure. here we report that pbcv-1 encodes a separate rna triphosphatase (rtp) that catalyzes the initial step in cap synthesis: hyd ... | 2001 | 11160672 |
| chlorella viruses contain genes encoding a complete polyamine biosynthetic pathway. | two genes encoding the putative polyamine biosynthetic enzymes agmatine iminohydrolase (aih) and n-carbamoylputrescine amidohydrolase (cpa) were cloned from the chloroviruses pbcv-1, ny-2a and mt325. they were expressed in escherichia coli to form c-terminal (his)6-tagged proteins and the recombinant proteins were purified by ni2+-binding affinity chromatography. the biochemical properties of the two enzymes are similar to aih and cpa enzymes from arabidopsis thaliana and pseudomonas aeruginosa. ... | 2007 | 17101165 |
| algal-lytic activities encoded by chlorella virus cvk2. | using a halo assay with e. coli lysates expressing chlorella virus cvk2 genes on a cosmid contig, two different algal-lytic activities against chlorella strain nc64a cells were found to be encoded on the cvk2 genome. the gene for val-1, one of the two activities, encoded a 349-aa orf, which was homologous to pbcv-1 a215l and cvn1 cl-2. the val-1 gene was expressed at relatively early stages of the virus life cycle; transcripts and translation products appeared at 60 and 90 min postinfection, res ... | 2000 | 11062042 |
| characterization of a beta-1,3-glucanase encoded by chlorella virus pbcv-1. | sequence analysis of the 330-kb chlorella virus pbcv-1 genome revealed an open-reading frame, a94l, that encodes a protein with significant amino acid identity to glycoside hydrolase family 16 beta-1,3-glucanases. the a94l gene was cloned and the protein was expressed as a gst-a94l fusion protein in escherichia coli. the recombinant a94l protein hydrolyzed the beta-1,3-glucose polymer laminarin and had slightly less hydrolytic activity on beta-1,3-1, 4-glucose polymers, lichenan and barley beta- ... | 2000 | 11021991 |
| topoisomerase ii from chlorella virus pbcv-1. characterization of the smallest known type ii topoisomerase. | type ii topoisomerases, a family of enzymes that govern topological dna interconversions, are essential to many cellular processes in eukaryotic organisms. because no data are available about the functions of these enzymes in the replication of viruses that infect eukaryotic hosts, this led us to express and characterize the first topoisomerase ii encoded by one of such viruses. paramecium bursaria chlorella virus 1 (pbcv-1) infects certain chlorella-like green algae and encodes a 120-kda protei ... | 2000 | 10702252 |
| characterization of two chitinase genes and one chitosanase gene encoded by chlorella virus pbcv-1. | chlorella virus pbcv-1 encodes two putative chitinase genes, a181/182r and a260r, and one chitosanase gene, a292l. the three genes were cloned and expressed in escherichia coli. the recombinant a181/182r protein has endochitinase activity, recombinant a260r has both endochitinase and exochitinase activities, and recombinant a292l has chitosanase activity. transcription of a181/182r, a260r, and a292l genes begins at 30, 60, and 60 min p.i., respectively; transcription of all three genes continues ... | 1999 | 10544110 |
| chlorella virus pbcv-1 encodes a functional homospermidine synthase. | sequence analysis of the 330-kb genome of chlorella virus paramecium bursaria chlorella virus 1 (pbcv-1) revealed an open reading frame, a237r, that encodes a protein with 34% amino acid identity to homospermidine synthase from rhodopseudomonas viridis. expression of the a237r gene product in escherichia coli established that the recombinant enzyme catalyzes the nad(+)-dependent formation of homospermidine from two molecules of putrescine. the a237r gene is expressed late in pbcv-1 infection. bo ... | 1999 | 10544099 |
| evidence for 4-hydroxyproline in viral proteins. characterization of a viral prolyl 4-hydroxylase and its peptide substrates. | 4-hydroxyproline, the characteristic amino acid of collagens and collagen-like proteins in animals, is also found in certain proline-rich proteins in plants but has been believed to be absent from viral and bacterial proteins. we report here on the cloning and characterization from a eukaryotic algal virus, paramecium bursaria chlorella virus-1, of a 242-residue polypeptide, which shows distinct sequence similarity to the c-terminal half of the catalytic alpha subunits of animal prolyl 4-hydroxy ... | 1999 | 10428773 |
| the catalytic mechanism of a pyrimidine dimer-specific glycosylase (pdg)/abasic lyase, chlorella virus-pdg. | the repair of uv light-induced cyclobutane pyrimidine dimers can proceed via the base excision repair pathway, in which the initial step is catalyzed by dna glycosylase/abasic (ap) lyases. the prototypical enzyme studied for this pathway is endonuclease v from the bacteriophage t4 (t4 bacteriophage pyrimidine dimer glycosylase (t4-pdg)). the first homologue for t4-pdg has been found in a strain of chlorella virus (strain paramecium bursaria chlorella virus-1), which contains a gene that predicts ... | 1999 | 10092668 |
| adherence of the gram-positive bacterium ruminococcus albus to cellulose and identification of a novel form of cellulose-binding protein which belongs to the pil family of proteins. | the adherence of ruminococcus albus 8 to crystalline cellulose was studied, and an affinity-based assay was also used to identify candidate cellulose-binding protein(s). bacterial adherence in cellulose-binding assays was significantly increased by the inclusion of either ruminal fluid or micromolar concentrations of both phenylacetic and phenylpropionic acids in the growth medium, and the addition of carboxymethylcellulose (cmc) to assays decreased the adherence of the bacterium to cellulose. a ... | 1998 | 9811650 |
| chlorella virus pbcv-1 encodes functional glutamine: fructose-6-phosphate amidotransferase and udp-glucose dehydrogenase enzymes. | dna sequence analysis of the 330-kb chlorella virus pbcv-1 genome unexpectedly revealed several open reading frames which encode proteins that are homologous to sugar-manipulating enzymes including glutamine:fructose-6-phosphate amidotransferase (gfat), udp-glucose dehydrogenase (udp-glcdh), and hyaluronan synthase (has). pbcv-1 genes encoding the putative gfat and udp-glcdh enzymes were expressed in escherichia coli, and both recombinant proteins have the predicted enzyme activity in cell free ... | 1998 | 9792849 |
| chlorella virus pyrimidine dimer glycosylase excises ultraviolet radiation- and hydroxyl radical-induced products 4,6-diamino-5-formamidopyrimidine and 2,6-diamino-4-hydroxy-5-formamidopyrimidine from dna. | a dna glycosylase specific for uv radiation-induced pyrimidine dimers has been identified from the chlorella virus paramecium bursaria chlorella virus-1. this enzyme (chlorella virus pyrimidine dimer glycosylase [cv-pdg]) exhibits a 41% amino acid identity with endonuclease v from bacteriophage t4 (t4 pyrimidine dimer glycosylase [t4-pdg]), which is also specific for pyrimidine dimers. however, cv-pdg possesses a higher catalytic efficiency and broader substrate specificity than t4-pdg. the latt ... | 2002 | 11883607 |
| viral ion channels: structure and function. | viral ion channels are short auxiliary membrane proteins with a length of ca. 100 amino acids. they are found in enveloped viruses from influenza a, influenza b and influenza c (orthomyxoviridae), and the human immunodeficiency virus type 1 (hiv-1, retroviridae). the channels are called m2 (influenza a), nb (influenza b), cm2 (influenza c) and vpu (hiv-1). recently, in paramecium bursaria chlorella virus (pbcv-1, phycodnaviridae), a k+ selective ion channel has been discovered. the viral channel ... | 2002 | 11988179 |
| site-specific dna cleavage by chlorella virus topoisomerase ii. | the dna cleavage reaction of topoisomerase ii is central to the catalytic activity of the enzyme and is the target for a number of important anticancer drugs. unfortunately, efforts to characterize this fundamental reaction have been limited by the low levels of dna breaks normally generated by the enzyme. recently, however, a type ii topoisomerase with an extraordinarily high intrinsic dna cleavage activity was isolated from chlorella virus pbcv-1. to further our understanding of this enzyme, t ... | 2002 | 12269818 |
| ornithine decarboxylase encoded by chlorella virus pbcv-1. | sequence analysis of the 330-kb genome of chlorella virus pbcv-1 revealed an open reading frame, a207r, which encodes a protein with 37-41% amino acid identity to ornithine decarboxylase (odc) from many eukaryotic organisms. the a207r gene was cloned and the protein was expressed as a his-a207r fusion protein in escherichia coli. the recombinant protein catalyzes pyridoxal 5'-phosphate-dependent decarboxylation of ornithine to putrescine, the first step in the polyamine biosynthetic pathway. the ... | 2002 | 12359457 |
| the structure and evolution of the major capsid protein of a large, lipid-containing dna virus. | paramecium bursaria chlorella virus type 1 (pbcv-1) is a very large, icosahedral virus containing an internal membrane enclosed within a glycoprotein coat consisting of pseudohexagonal arrays of trimeric capsomers. each capsomer is composed of three molecules of the major capsid protein, vp54, the 2.0-a resolution structure of which is reported here. four n-linked and two o-linked glycosylation sites were identified. the n-linked sites are associated with nonstandard amino acid motifs as a resul ... | 2002 | 12411581 |
| paramecium bursaria chlorella virus 1 encodes two enzymes involved in the biosynthesis of gdp-l-fucose and gdp-d-rhamnose. | at least three structural proteins in paramecium bursaria chlorella virus (pbcv-1) are glycosylated, including the major capsid protein vp54. however, unlike other glycoprotein-containing viruses that use host-encoded enzymes in the endoplasmic reticulum-golgi to glycosylate their proteins, pbcv-1 encodes at least many, if not all, of the glycosyltransferases used to glycosylate its structural proteins. as described here, pbcv-1 also encodes two open reading frames that resemble bacterial and ma ... | 2003 | 12679342 |
| characterization of a chlorella virus pbcv-1 encoded ribonuclease iii. | sequence analysis of the 330-kb genome of chlorella virus pbcv-1 revealed an open reading frame, a464r, which encodes a protein with 30-35% amino acid identity to ribonuclease iii (rnase iii) from many bacteria. the a464r gene was cloned and the protein was expressed in escherichia coli using the chitin-binding intein system. the recombinant pbcv-1 rnase iii cleaves model dsrna substrates, in a mg(2+)-dependent manner, into a defined set of products. the substrate cleavage specificity overlaps, ... | 2003 | 14675626 |
| functional analysis of fad-dependent thymidylate synthase thyx from paramecium bursaria chlorella virus-1. | sequence analysis of the 330-kb double-stranded dna genome of paramecium bursaria chlorella virus-1 revealed an open reading frame a674r that encodes a protein with up to 53% amino acid identity to a recently discovered new class of thymidylate synthases, called thyx. unlike the traditional thymidylate synthase, thya, that uses methylenetetrahydrofolate (ch(2)h(4)folate) as both a source of the methylene group and the reductant, ch(2)h(4)folate only supplies the methylene group in thyx-catalyzed ... | 2004 | 15471872 |
| insights into assembly from structural analysis of bacteriophage prd1. | the structure of the membrane-containing bacteriophage prd1 has been determined by x-ray crystallography at about 4 a resolution. here we describe the structure and location of proteins p3, p16, p30 and p31. different structural proteins seem to have specialist roles in controlling virus assembly. the linearly extended p30 appears to nucleate the formation of the icosahedral facets (composed of trimers of the major capsid protein, p3) and acts as a molecular tape-measure, defining the size of th ... | 2004 | 15525981 |
| chlorella virus marburg topoisomerase ii: high dna cleavage activity as a characteristic of chlorella virus type ii enzymes. | although the formation of a covalent enzyme-cleaved dna complex is a prerequisite for the essential functions of topoisomerase ii, this reaction intermediate has the potential to destabilize the genome. consequently, all known eukaryotic type ii enzymes maintain this complex at a low steady-state level. recently, however, a novel topoisomerase ii was discovered in paramecium bursaria chlorella virus-1 (pbcv-1) that has an exceptionally high dna cleavage activity [fortune et al. (2001) j. biol. c ... | 2005 | 15751965 |
| ability of viral topoisomerase ii to discern the handedness of supercoiled dna: bimodal recognition of dna geometry by type ii enzymes. | previous studies with human and bacterial topoisomerases suggest that the type ii enzyme utilizes two distinct mechanisms to recognize the handedness of dna supercoils. it has been proposed that the ability of some type ii enzymes, such as human topoisomerase iialpha and escherichia coli topoisomerase iv, to distinguish supercoil geometry during dna relaxation is mediated by elements in the variable c-terminal domain of the protein. in contrast, the ability of human topoisomerase iialpha and top ... | 2006 | 16981727 |
| sequence and annotation of the 288-kb atcv-1 virus that infects an endosymbiotic chlorella strain of the heliozoon acanthocystis turfacea. | acanthocystis turfacea chlorella virus (atcv-1), a prospective member of the family phycodnaviridae, genus chlorovirus, infects a unicellular, eukaryotic, chlorella-like green alga, chlorella sag 3.83, that is a symbiont in the heliozoon a. turfacea. the 288,047-bp atcv-1 genome is the first virus to be sequenced that infects chlorella sag 3.83. atcv-1 contains 329 putative protein-encoding and 11 trna-encoding genes. the protein-encoding genes are almost evenly distributed on both strands and i ... | 2007 | 17276475 |
| differential role of nadp+ and nadph in the activity and structure of gdp-d-mannose 4,6-dehydratase from two chlorella viruses. | gdp-d-mannose 4,6-dehydratase (gmd) is a key enzyme involved in the synthesis of 6-deoxyhexoses in prokaryotes and eukaryotes. paramecium bursaria chlorella virus-1 (pbcv-1) encodes a functional gmd, which is unique among characterized gmds because it also has a strong stereospecific nadph-dependent reductase activity leading to gdp-d-rhamnose formation (tonetti, m., zanardi, d., gurnon, j., fruscione, f., armirotti, a., damonte, g., sturla, l., de flora, a., and van etten, j.l. (2003) j. biol. ... | 2008 | 17974560 |
| cloning, characterization and expression analysis of nucleotide metabolism-related genes of mycobacteriophage l5. | the genomes of mycobacteriophages of the l5 family, which includes the lytic phage d29, contain several genes putatively linked to nucleotide-metabolizing functions. two such genes, 48 and 50, encoding thymidylate synthase and ribonucleotide reductase (rnr), respectively, were overexpressed in escherichia coli and the recombinant proteins were biochemically characterized. it was established that gp50 was a class ii rnr having properties similar to that of the corresponding enzyme from lactobacil ... | 2008 | 18248423 |
| phylogenetic analysis of members of the phycodnaviridae virus family, using amplified fragments of the major capsid protein gene. | algal viruses are considered ecologically important by affecting host population dynamics and nutrient flow in aquatic food webs. members of the family phycodnaviridae are also interesting due to their extraordinary genome size. few algal viruses in the phycodnaviridae family have been sequenced, and those that have been have few genes in common and low gene homology. it has hence been difficult to design general pcr primers that allow further studies of their ecology and diversity. in this stud ... | 2008 | 18359826 |
| [identification of chlorella viruses in paramecium bursaria clones by pulse-field electrophoresis]. | the ciliates paramecium bursaria contain endosymbiotic green algae chlorella spp. in their cytoplasm. the algae isolated from p. bursaria are sensitive to large dna-containing viruses of the family phycodnaviridae. the type virus of this family is pbcv-1 (paramecium bursaria chlorella virus). investigation of the total dna of p. bursaria clones by pulse-field electrophoresis (pep) revealed a pronounced band on pep profiles of some p. bursaria clones; the band was formed by dna molecules of appro ... | 2008 | 19004349 |
| the capsid proteins of a large, icosahedral dsdna virus. | chilo iridescent virus (civ) is a large (approximately 1850 a diameter) insect virus with an icosahedral, t=147 capsid, a double-stranded dna (dsdna) genome, and an internal lipid membrane. the structure of civ was determined to 13 a resolution by means of cryoelectron microscopy (cryoem) and three-dimensional image reconstruction. a homology model of p50, the civ major capsid protein (mcp), was built based on its amino acid sequence and the structure of the homologous paramecium bursaria chlore ... | 2009 | 19027752 |
| chlorella virus atcv-1 encodes a functional potassium channel of 82 amino acids. | chlorella virus pbcv-1 (paramecium bursaria chlorella virus-1) encodes the smallest protein (94 amino acids, named kcv) previously known to form a functional k+ channel in heterologous systems. in this paper, we characterize another chlorella virus encoded k+ channel protein (82 amino acids, named atcv-1 kcv) that forms a functional channel in xenopus oocytes and rescues saccharomyces cerevisiae mutants that lack endogenous k+ uptake systems. compared with the larger pbcv-1 kcv, atcv-1 kcv lacks ... | 2009 | 19267691 |
| an icosahedral algal virus has a complex unique vertex decorated by a spike. | paramecium bursaria chlorella virus-1 is an icosahedrally shaped, 1,900-a-diameter virus that infects unicellular eukaryotic green algae. a 5-fold symmetric, 3d reconstruction using cryoelectron microscopy images has now shown that the quasiicosahedral virus has a unique vertex, with a pocket on the inside and a spike structure on the outside of the capsid. the pocket might contain enzymes for use in the initial stages of infection. the unique vertex consists of virally coded proteins, some of w ... | 2009 | 19541619 |
| viral-encoded enzymes that target host chromatin functions. | ever since their existence, there has been an everlasting arms race between viruses and their host cells. host cells have developed numerous strategies to silence viral gene expression whereas viruses always find their ways to overcome these obstacles. recent studies show that viruses have also evolved to take full advantage of existing cellular chromatin components to activate or repress its own genes when needed. while in most cases viruses encode certain proteins to recruit or inhibit cellula ... | 2010 | 19716451 |
| chlorovirus skp1-binding ankyrin repeat protein interplay and mimicry of cellular ubiquitin ligase machinery. | the ubiquitin-proteasome system is targeted by many viruses that have evolved strategies to redirect host ubiquitination machinery. members of the genus chlorovirus are proposed to share an ancestral lineage with a broader group of related viruses, nucleo-cytoplasmic large dna viruses (ncldv). chloroviruses encode an skp1 homolog and ankyrin repeat (ank) proteins. several chlorovirus-encoded ank repeats contain c-terminal domains characteristic of cellular f-boxes or related ncldv chordopox pran ... | 2014 | 25253343 |
| viral proteins function as ion channels. | viral ion channels are short membrane proteins with 50-120 amino acids and play an important role either in regulating virus replication, such as virus entry, assembly and release or modulating the electrochemical balance in the subcellular compartments of host cells. this review summarizes the recent advances in viral encoded ion channel proteins (or viroporins), including pbcv-1 kcv, influenza m2, hiv-1 vpu, hcv p7, picornavirus 2b, and coronavirus e and 3a. we focus on their function and mech ... | 2011 | 20478263 |
| tat-mediated delivery of a dna repair enzyme to skin cells rapidly initiates repair of uv-induced dna damage. | uv light causes dna damage in skin cells, leading to more than one million cases of non-melanoma skin cancer diagnosed annually in the united states. although human cells possess a mechanism (nucleotide excision repair) to repair uv-induced dna damage, mutagenesis still occurs when dna is replicated before repair of these photoproducts. although human cells have all the enzymes necessary to complete an alternate repair pathway, base excision repair (ber), they lack a dna glycosylase that can ini ... | 2010 | 20927123 |
| modulation of the processive abasic site lyase activity of a pyrimidine dimer glycosylase. | the repair of cis-syn cyclobutane pyrimidine dimers (cpds) can be initiated via the base excision repair (ber) pathway, utilizing pyrimidine dimer-specific dna glycosylase/lyase enzymes (pdgs). however, prior to incision at lesion sites, these enzymes bind to non-damaged dnas through charge-charge interactions. following initial binding to dna containing multiple lesions, the enzyme incises at most of these sites prior to dissociation. if a subset of these lesions are in close proximity, cluster ... | 2011 | 21889915 |
| characterization of viruses infecting a eukaryotic chlorella-like green alga. | nineteen plaque-forming viruses of the unicellular, eukaryotic chlorella-like green alga, strain nc64a, were isolated from various geographic regions in the united states and characterized. like the previously described virus, pbcv-1, all of the new viruses were large polyhedrons, sensitive to chloroform, and contained large dsdna genomes of ca. 300 kbp. all of the viral dnas contained 5-methyldeoxycytidine which varied from 0.1 to 47% of the deoxycytidine. in addition, 10 of the viral dnas cont ... | 2010 | 3006334 |
| chloroviruses encode a bifunctional dcmp-dctp deaminase that produces two key intermediates in dttp formation. | the chlorovirus pbcv-1, like many large double-stranded dna-containing viruses, contains several genes that encode putative proteins involved in nucleotide biosynthesis. this report describes the characterization of the pbcv-1 dcmp deaminase, which produces dump, a key intermediate in the synthesis of dttp. as predicted, the recombinant protein has dcmp deaminase activity that is activated by dctp and inhibited by dttp. unexpectedly, however, the viral enzyme also has dctp deaminase activity, pr ... | 2007 | 17475641 |
| chlorovirus-mediated membrane depolarization of chlorella alters secondary active transport of solutes. | paramecium bursaria chlorella virus 1 (pbcv-1) is the prototype of a family of large, double-stranded dna, plaque-forming viruses that infect certain eukaryotic chlorella-like green algae from the genus chlorovirus. pbcv-1 infection results in rapid host membrane depolarization and potassium ion release. one interesting feature of certain chloroviruses is that they code for functional potassium ion-selective channel proteins (kcv) that are considered responsible for the host membrane depolarizat ... | 2008 | 18842725 |
| structure and function of a chlorella virus-encoded glycosyltransferase. | paramecium bursaria chlorella virus-1 encodes at least five putative glycosyltransferases that are probably involved in the synthesis of the glycan components of the viral major capsid protein. the 1.6 a crystal structure of one of these glycosyltransferases (a64r) has a mixed alpha/beta fold containing a central, six-stranded beta sheet flanked by alpha helices. crystal structures of a64r, complexed with udp, cmp, or gdp, established that only udp bound to a64r in the presence of mn(2+), consis ... | 2007 | 17850743 |
| characterization of a monothiol glutaredoxin encoded by chlorella virus pbcv-1. | annotation of the 330-kb chlorella virus pbcv-1 genome identified a 237 nucleotide gene (a438l) that codes for a protein with approximately 35% amino acid identity to glutaredoxins (grx) found in other organisms. the pbcv-1 protein resembles classical grxs in both size (9 kda) and location of the active site (n-terminus). however, the pbcv-1 grx is unusual because it contains a monothiol active site (cpys) rather than the typical dithiol active site (cpyc). to examine this unique active site, fo ... | 2009 | 19697117 |
| impact of the c-terminal domain of topoisomerase iialpha on the dna cleavage activity of the human enzyme. | the enzymatic function of the c-terminal domain of eukaryotic topoisomerase ii is not well defined. this region of the enzyme is highly variable and hydrophilic and contains nuclear localization signals and phosphorylation sites. in contrast to eukaryotic topoisomerase ii, type ii enzymes from chlorella virus completely lack the c-terminal domain. these viral enzymes are characterized by a robust dna cleavage activity, high coordination between their two active site tyrosyl residues, and reduced ... | 2005 | 16114891 |
| dna methylation impacts the cleavage activity of chlorella virus topoisomerase ii. | topoisomerase ii from paramecium bursaria chlorella virus-1 (pbcv-1) and chlorella virus marburg-1 (cvm-1) displays an extraordinarily high in vitro dna cleavage activity that is 30-50 times higher than that of human topoisomerase iialpha. this remarkable scission activity may reflect a unique role played by the type ii enzyme during the viral life cycle that extends beyond the normal control of dna topology. alternatively, but not mutually exclusively, it may reflect an adaptation to some aspec ... | 2005 | 16285742 |
| genetic diversity of algal viruses which lyse the photosynthetic picoflagellate micromonas pusilla (prasinophyceae). | the genetic similarity among eight clones of micromonas pusilla virus (mpv) isolated from five geographic locations was measured by dna hybridization. our objective was to explore the existence of genetically distinct populations of mpv by comparing the similarity among mpvs isolated from a single water sample to the similarity among viruses isolated from geographically distant locations. the highest and lowest similarities we observed were 70% (plusmn) 1.1% (mean (plusmn) standard error [se], n ... | 1995 | 16535105 |
| structure of a197 from sulfolobus turreted icosahedral virus: a crenarchaeal viral glycosyltransferase exhibiting the gt-a fold. | sulfolobus turreted icosahedral virus (stiv) was the first icosahedral virus characterized from an archaeal host. it infects sulfolobus species that thrive in the acidic hot springs (ph 2.9 to 3.9 and 72 to 92 degrees c) of yellowstone national park. the overall capsid architecture and the structure of its major capsid protein are very similar to those of the bacteriophage prd1 and eukaryotic viruses paramecium bursaria chlorella virus 1 and adenovirus, suggesting a viral lineage that predates t ... | 2006 | 16840342 |
| footprinting of chlorella virus dna ligase bound at a nick in duplex dna. | the 298-amino acid atp-dependent dna ligase of chlorella virus pbcv-1 is the smallest eukaryotic dna ligase known. the enzyme has intrinsic specificity for binding to nicked duplex dna. to delineate the ligase-dna interface, we have footprinted the enzyme binding site on dna and the dna binding site on ligase. the size of the exonuclease iii footprint of ligase bound a single nick in duplex dna is 19-21 nucleotides. the footprint is asymmetric, extending 8-9 nucleotides on the 3'-oh side of the ... | 1999 | 10318816 |
| crystallization of the rna guanylyltransferase of chlorella virus pbcv-1. | rna guanylyltransferase, or capping enzyme (e.c. 2.7.7.50) catalyzes the transfer of gmp from gtp to diphosphate-terminated rna to form the cap structure gpppn. chlorella virus capping enzyme expressed in e. coli has been purified, treated with gtp and crystallized. x-ray diffraction data have been collected from these crystals as well as for a mercury derivative obtained by soaking the crystals in thimerosal. selenomethionine rna guanylyltransferase was purified and crystallized in a similar fa ... | 1997 | 15299921 |
| efficient in situ detection of mrnas using the chlorella virus dna ligase for padlock probe ligation. | padlock probes are single-stranded dna molecules that are circularized upon hybridization to their target sequence by a dna ligase. in the following, the circulated padlock probes are amplified and detected with fluorescently labeled probes complementary to the amplification product. the hallmark of padlock probe assays is a high detection specificity gained by the ligation reaction. concomitantly, the ligation reaction is the largest drawback for a quantitative in situ detection of mrnas due to ... | 2017 | 27879431 |
| characterization of a new chlorovirus type with permissive and non-permissive features on phylogenetically related algal strains. | a previous report indicated that prototype chlorovirus pbcv-1 replicated in two chlorella variabilis algal strains, nc64a and syngen 2-3, that are ex-endosymbionts isolated from the protozoan paramecium bursaria. surprisingly, plaque-forming viruses on syngen 2-3 lawns were often higher than on nc64a lawns from indigenous water samples. these differences led to the discovery of viruses that exclusively replicate in syngen 2-3 cells, named only syngen (osy) viruses. osy-ne5, the prototype virus f ... | 2017 | 27816636 |
| influence of iron-doped apatite nanoparticles on viral infection examined in bacterial versus algal systems. | the centers for disease control and prevention have estimated that each year, two million people in the united states become infected with antibiotic-resistant bacteria, of which, approximately 23000 die as a direct result of these infections. phage therapy, or the treatment of bacterial infection by specific, antagonistic viruses, provides one alternative to traditional antibiotics. bacteriophages, or phages, are bacteria-specific viruses that possess biological traits that allow for not only t ... | 2016 | 27775532 |
| thermal stability and binding energetics of thymidylate synthase thyx. | the bacterial thymidylate synthase thyx is a multisubstrate flavoenzyme that takes part in the de novo synthesis of thymidylate in a variety of microorganisms. herein we study the effect of fad and dump binding on the thermal stability of wild type (wt) thyx from the mesophilic paramecium bursaria chlorella virus-1 (pbcv-1) and from the thermophilic bacterium thermotoga maritima (tmthyx), and from two variants of tmthyx, y91f and s88w, using differential scanning calorimetry. the energetics unde ... | 2016 | 27268384 |
| noninvasive measurement of electrical events associated with a single chlorovirus infection of a microalgal cell. | chlorovirus paramecium bursaria chlorella virus 1 (pbcv-1) contains a viral-encoded k(+) channel imbedded in its internal membrane, which triggers host plasma membrane depolarization during virus infection. this early stage of infection was monitored at high resolution by recording the cell membrane depolarization of a single chlorella cell during infection by a single pbcv-1 particle. the measurement was achieved by depositing the cells onto a network of one-dimensional necklaces of au nanopart ... | 2016 | 27139597 |
| the autonomous glycosylation of large dna viruses. | glycosylation of surface molecules is a key feature of several eukaryotic viruses, which use the host endoplasmic reticulum/golgi apparatus to add carbohydrates to their nascent glycoproteins. in recent years, a newly discovered group of eukaryotic viruses, belonging to the nucleo-cytoplasmic large dna virus (ncldv) group, was shown to have several features that are typical of cellular organisms, including the presence of components of the glycosylation machinery. starting from initial observati ... | 2015 | 26690138 |
| virus-host interactions: insights from the replication cycle of the large paramecium bursaria chlorella virus. | the increasing interest in cytoplasmic factories generated by eukaryotic-infecting viruses stems from the realization that these highly ordered assemblies may contribute fundamental novel insights to the functional significance of order in cellular biology. here, we report the formation process and structural features of the cytoplasmic factories of the large dsdna virus paramecium bursaria chlorella virus 1 (pbcv-1). by combining diverse imaging techniques, including scanning transmission elect ... | 2016 | 26248343 |
| dynamic attachment of chlorovirus pbcv-1 to chlorella variabilis. | chloroviruses infect their hosts by specifically binding to and degrading the cell wall of their algal hosts at the site of attachment, using an intrinsic digesting enzyme(s). chlorovirus pbcv-1 stored as a lysate survived longer than virus alone, suggesting virus attachment to cellular debris may be reversible. ghost cells (algal cells extracted with methanol) were used as a model to study reversibility of pbcv-1 attachment because ghost cells are as susceptible to attachment and wall digestion ... | 2014 | 25240455 |
| chlorovirus pbcv-1 encodes an active copper-zinc superoxide dismutase. | superoxide dismutases (sods) are metalloproteins that protect organisms from toxic reactive oxygen species by catalyzing the conversion of superoxide anion to hydrogen peroxide and molecular oxygen. chlorovirus pbcv-1 encodes a 187-amino-acid protein that resembles a cu-zn sod with all of the conserved amino acid residues for binding copper and zinc (named cvsod). cvsod has an internal met that results in a 165-amino-acid protein (named tcvsod). both cvsod and tcvsod recombinant proteins inhibit ... | 2014 | 25142578 |
| deep rna sequencing reveals hidden features and dynamics of early gene transcription in paramecium bursaria chlorella virus 1. | paramecium bursaria chlorella virus 1 (pbcv-1) is the prototype of the genus chlorovirus (family phycodnaviridae) that infects the unicellular, eukaryotic green alga chlorella variabilis nc64a. the 331-kb pbcv-1 genome contains 416 major open reading frames. a mrna-seq approach was used to analyze pbcv-1 transcriptomes at 6 progressive times during the first hour of infection. the alignment of 17 million reads to the pbcv-1 genome allowed the construction of single-base transcriptome maps. signi ... | 2014 | 24608750 |
| global analysis of chlorella variabilis nc64a mrna profiles during the early phase of paramecium bursaria chlorella virus-1 infection. | the pbcv-1/chlorella variabilis nc64a system is a model for studies on interactions between viruses and algae. here we present the first global analyses of algal host transcripts during the early stages of infection, prior to virus replication. during the course of the experiment stretching over 1 hour, about a third of the host genes displayed significant changes in normalized mrna abundance that either increased or decreased compared to uninfected levels. the population of genes with significa ... | 2014 | 24608695 |
| substrate interaction dynamics and oxygen control in the active site of thymidylate synthase thyx. | thymidylate synthase thyx, required for dna synthesis in many pathogenic bacteria, is considered a promising antimicrobial target. it binds fad and three substrates, producing dtmp (2'-deoxythymidine-5'-monophosphate) from dump (2'-deoxyuridine-5'-monophosphate). however, thyx proteins also act as nadph oxidase by reacting directly with o2. in the present study we investigated the dynamic interplay between the substrates and their role in competing with this wasteful and potentially harmful oxid ... | 2014 | 24422556 |
| efficient dna ligation in dna-rna hybrid helices by chlorella virus dna ligase. | single-stranded dna molecules (ssdna) annealed to an rna splint are notoriously poor substrates for dna ligases. herein we report the unexpectedly efficient ligation of rna-splinted dna by chlorella virus dna ligase (pbcv-1 dna ligase). pbcv-1 dna ligase ligated ssdna splinted by rna with kcat ≈ 8 x 10(-3) s(-1) and k(m) < 1 nm at 25 °c under conditions where t4 dna ligase produced only 5'-adenylylated dna with a 20-fold lower kcat and a k(m) ≈ 300 nm. the rate of ligation increased with additio ... | 2014 | 24203707 |
| enzymatic synthesis of rnas capped with nucleotide analogues reveals the molecular basis for substrate selectivity of rna capping enzyme: impacts on rna metabolism. | rna cap binding proteins have evolved to specifically bind to the n7-methyl guanosine cap structure found at the 5' ends of eukaryotic mrnas. the specificity of rna capping enzymes towards gtp for the synthesis of this structure is therefore crucial for mrna metabolism. the fact that ribavirin triphosphate was described as a substrate of a viral rna capping enzyme, raised the possibility that rnas capped with nucleotide analogues could be generated in cellulo. owing to the fact that this prospec ... | 2013 | 24086504 |
| a virus-encoded potassium ion channel is a structural protein in the chlorovirus paramecium bursaria chlorella virus 1 virion. | most chloroviruses encode small k(+) channels, which are functional in electrophysiological assays. the experimental finding that initial steps in viral infection exhibit the same sensitivity to channel inhibitors as the viral k(+) channels has led to the hypothesis that the channels are structural proteins located in the internal membrane of the virus particles. this hypothesis was questioned recently because proteomic studies failed to detect the channel protein in virions of the prototype chl ... | 2013 | 23918407 |
| structure of n-linked oligosaccharides attached to chlorovirus pbcv-1 major capsid protein reveals unusual class of complex n-glycans. | the major capsid protein vp54 from the prototype chlorovirus paramecium bursaria chlorella virus 1 (pbcv-1) contains four asn-linked glycans. the structure of the four n-linked oligosaccharides and the type of substitution at each glycosylation site was determined by chemical, spectroscopic, and spectrometric analyses. vp54 glycosylation is unusual in many ways, including: (i) unlike most viruses, pbcv-1 encodes most, if not all, of the machinery to glycosylate its major capsid protein; (ii) the ... | 2013 | 23918378 |
| a novel potassium channel encoded by ectocarpus siliculosus virus. | kcv, the first identified viral potassium channel encoded by the green algae paramecium bursaria chlorella virus (pbcv-1), conducted k(+) selective currents when expressed in heterologous systems. this k(+) channel was proposed to be important for pbcv-1 infection and replication. in the present study, we identified and functionally characterized a novel k(+) channel kesv, encoded by ectocarpus siliculosus virus that infects filamentous marine brown algae. kesv encodes a protein of 124 amino aci ... | 2005 | 15607752 |
| phycodnaviridae--large dna algal viruses. | members and prospective members of the family phycodnaviridae are large icosahedral, dsdna (180 to 560 kb) viruses that infect eukaryotic algae. the genomes of two phycodnaviruses have been sequenced: the 331 kb genome of paramecium bursaria chlorella virus (pbcv-1) and more recently, the 336 kb genome of the ectocarpus siliculosus virus (esv-1). esv-1 has approximately 231 protein-encoding genes whereas, the slightly smaller pbcv-1 genome has 11 trna genes and approximately 375 protein-encoding ... | 2002 | 12181671 |
| the complete dna sequence of the ectocarpus siliculosus virus esv-1 genome. | the ectocarpus siliculosus virus-1, esv-1, is the type-species of a genus of phycodnaviridae, the phaeoviruses, infecting marine filamentous brown algae. the esv-1 genome of 335,593 bp contains tandem and dispersed repetitive elements in addition to a large number of open reading frames of which 231 are currently counted as genes. many genes can be assigned to functional groups involved in dna synthesis, dna integration, transposition, and polysaccharide metabolism. furthermore, esv-1 contains c ... | 2001 | 11504547 |
| evaluation of higher plant virus resistance genes in the green alga, chlorella variabilis nc64a, during the early phase of infection with paramecium bursaria chlorella virus-1. | with growing industrial interest in algae plus their critical roles in aquatic systems, the need to understand the effects of algal pathogens is increasing. we examined a model algal host-virus system, chlorella variabilis nc64a and virus, pbcv-1. c. variabilis encodes 375 homologs to genes involved in rna silencing and in response to virus infection in higher plants. illumina rna-seq data showed that 325 of these homologs were expressed in healthy and early pbcv-1 infected (≤60min) cells. for e ... | 2013 | 23701839 |
| towards defining the chloroviruses: a genomic journey through a genus of large dna viruses. | giant viruses in the genus chlorovirus (family phycodnaviridae) infect eukaryotic green microalgae. the prototype member of the genus, paramecium bursaria chlorella virus 1, was sequenced more than 15 years ago, and to date there are only 6 fully sequenced chloroviruses in public databases. presented here are the draft genome sequences of 35 additional chloroviruses (287 - 348 kb/319 - 381 predicted protein encoding genes) collected across the globe; they infect one of three different green alga ... | 2013 | 23497343 |
| phycodnavirus potassium ion channel proteins question the virus molecular piracy hypothesis. | phycodnaviruses are large dsdna, algal-infecting viruses that encode many genes with homologs in prokaryotes and eukaryotes. among the viral gene products are the smallest proteins known to form functional k(+) channels. to determine if these viral k(+) channels are the product of molecular piracy from their hosts, we compared the sequences of the k(+) channel pore modules from seven phycodnaviruses to the k(+) channels from chlorella variabilis and ectocarpus siliculosus, whose genomes have rec ... | 2012 | 22685610 |
| paramecium bursaria chlorella virus 1 encodes a polyamine acetyltransferase. | paramecium bursaria chlorella virus 1 (pbcv-1), a large dna virus that infects green algae, encodes a histone h3 lysine 27-specific methyltransferase that functions in global transcriptional silencing of the host. pbcv-1 has another gene a654l that encodes a protein with sequence similarity to the gcn5 family histone acetyltransferases. in this study, we report a 1.5 å crystal structure of pbcv-1 a654l in a complex with coenzyme a. the structure reveals a unique feature of a654l that precludes i ... | 2012 | 22277659 |
| chloroviruses: not your everyday plant virus. | viruses infecting higher plants are among the smallest viruses known and typically have four to ten protein-encoding genes. by contrast, many viruses that infect algae (classified in the virus family phycodnaviridae) are among the largest viruses found to date and have up to 600 protein-encoding genes. this brief review focuses on one group of plaque-forming phycodnaviruses that infect unicellular chlorella-like green algae. the prototype chlorovirus pbcv-1 has more than 400 protein-encoding gen ... | 2012 | 22100667 |
| atomic force microscopy investigation of a chlorella virus, pbcv-1. | a virus pbcv-1, which infects certain fresh water algae and has been shown by transmission and cryo-electron microscopy to exist as a triskaidecahedron, was imaged using atomic force microscopy (afm). from afm the particles have diameters of about 190nm and the overall structure is in all important respects consistent with existing models. the surface lattice of the virion is composed of trimeric capsid proteins distributed according to p3 symmetry to create a honeycomb arrangement of raised edg ... | 2005 | 15721579 |
| structures of giant icosahedral eukaryotic dsdna viruses. | in the last twenty years, numerous giant, dsdna, icosahedral viruses have been discovered and assigned to the nucleocytoplasmic large dsdna virus (ncldv) clade. the major capsid proteins of these viruses consist of two consecutive jelly-roll domains, assembled into trimers, with pseudo 6-fold symmetry. the capsomers are assembled into arrays that have either p6 (as in paramecium bursaria chlorella virus-1) or p3 symmetry (as in mimivirus). most of the ncldv viruses have a membrane that separates ... | 2011 | 21909343 |
| initial events associated with virus pbcv-1 infection of chlorella nc64a. | chlorella viruses (or chloroviruses) are very large, plaque-forming viruses. the viruses are multilayered structures containing a large double-stranded dna genome, a lipid bilayered membrane, and an outer icosahedral capsid shell. the viruses replicate in certain isolates of the coccal green alga, chlorella. sequence analysis of the 330-kbp genome of paramecium bursaria chlorella virus 1 (pbcv-1), the prototype of the virus family phycodnaviridae, reveals <365 protein-encoding genes and 11 trna ... | 2010 | 21152366 |
| isolation of the phycodnavirus pbcv-1 by biological laser printing. | the phycodnaviridae family of viruses is diverse genetically but similar morphologically. these viruses infect eukaryotic algal hosts from both fresh and marine waters, and are an important component of aqueous environments. they play important roles in the dynamics of algal blooms, nutrient cycling, algal community structure, and possibly gene transfer between organisms. as such, it is important to identify new viruses within the phycodnaviridae family. biological laser printing (biolp) was use ... | 2010 | 20399229 |
| microarray analysis of paramecium bursaria chlorella virus 1 transcription. | paramecium bursaria chlorella virus 1 (pbcv-1), a member of the family phycodnaviridae, is a large double-stranded dna, plaque-forming virus that infects the unicellular green alga chlorella sp. strain nc64a. the 330-kb pbcv-1 genome is predicted to encode 365 proteins and 11 trnas. to monitor global transcription during pbcv-1 replication, a microarray containing 50-mer probes to the pbcv-1 365 protein-encoding genes (cdss) was constructed. competitive hybridization experiments were conducted b ... | 2010 | 19828609 |
| fast and slow gating are inherent properties of the pore module of the k+ channel kcv. | kcv from the chlorella virus pbcv-1 is a viral protein that forms a tetrameric, functional k+ channel in heterologous systems. kcv can serve as a model system to study and manipulate basic properties of the k+ channel pore because its minimalistic structure (94 amino acids) produces basic features of ion channels, such as selectivity, gating, and sensitivity to blockers. we present a characterization of kcv properties at the single-channel level. in symmetric 100 mm k+, single-channel conductanc ... | 2009 | 19720961 |
| sequence-specific 1h n, 13c, and 15n backbone resonance assignments of the 34 kda paramecium bursaria chlorella virus 1 (pbcv1) dna ligase. | chlorella virus dna ligase (chvlig) is a minimal (298-amino acid) pluripotent atp-dependent ligase composed of three structural modules--a nucleotidyltransferase domain, an ob domain, and a beta-hairpin latch--that forms a circumferential clamp around nicked dna. chvlig provides an instructive model to understand the chemical and conformational steps of nick repair. here we report the assignment of backbone (13)c, (15)n, (1)h(n) resonances of this 34.2 kda protein, the first for a dna ligase in ... | 2009 | 19636951 |
| [the cell wall-degrading activities of lysin encoded by chlorella virus pbcv-1]. | lysin was isolated from chlorella nc64a lysate which was infected by chlorella virus pbcv-1. the enzyme property detection of lysin shows that it contains at least three enzyme activities: chitinase, chitosanase and beta-1, 3-glucanase. this is consistent with the compose of chlolrella cell wall. chitinase and chitosanase, especially chitinase plays a important role in the process of virus entry. one 52 kd chitinase, one 56 kd chitosanase and one 36 kd chitosanase were obtained after purified by ... | 2002 | 12557379 |