Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
|---|
| viruses of symbiotic chlorella-like algae isolated from paramecium bursaria and hydra viridis. | we previously reported that isolation of symbiotic chlorella-like algae from the florida strain of hydra viridis induced replication of a virus (designated hvcv-1) in the algae. we now report that isolation of symbiotic chlorella-like algae from four other sources of green hydra and one source of the protozoan paramecium bursaria also induced virus synthesis. algae from one of these hydra contained a virus identical to hvcv-1 (based on its rate of sedimentation, buoyant density, reaction to hvcv ... | 1982 | 16593198 |
| virus infection of culturable chlorella-like algae and dlevelopment of a plaque assay. | four distinct viruses with double-stranded dna are known to replicate in chlorella-like algae symbiotic with hydras and paramecia. an attempt was made to infect a number of cultured chlorella strains derived from invertebrate hosts with these viruses. one of the viruses, pbcv-1, replicated in two of the algal strains. restriction endonuclease analysis of the viral dna showed that the infectious progeny virus was identical to the input virus; thus, koch's postulates were fulfilled. viral infectio ... | 1983 | 17817937 |
| growth cycle of a virus, pbcv-1, that infects chlorella-like algae. | the growth and purification of milligram quantities of a large double-stranded dna virus, pbcv-1, which replicates in a chlorella-like alga is described. the virus had an adsorption rate constant of ca. 5 x 10(-9) ml/min, a latent period of 150 to 180 min, and a burst size of 200 to 350 pfus when the host was actively growing in the light. the eclipse period was 30 to 50 min shorter than the latent period. pbcv-1 also replicated in dark grown chlorella but the burst size was reduced ca. 50%. the ... | 1983 | 18638936 |
| infection of a chlorella-like alga with the virus, pbcv-1: ultrastructural studies. | ultrastructural studies revealed that the virus, pbcv-1, adsorbs to the surface of the chlorella-like green alga nc64a and enzymatically digests a portion of the host cell wall. the viral dna is then released into the interior of the cell leaving an empty capsid on the surface. thus uncoating of the viral genome occurs at the surface of its host. pbcv-1 also adsorbs to and digests the host wall of either heat-killed, methanol-extracted, or purified cell wall fragments. | 1984 | 6495652 |
| structural proteins and lipids in a virus, pbcv-1, which replicates in a chlorella-like alga. | pbcv-1, a large dsdna-containing virus which replicates in a chlorella-like green alga, is composed of approximately 64% protein, 25% dna, and 5-10% lipid on a weight basis. polyacrylamide gel electrophoresis of the dissociated virus particle resolves 50 to 60 proteins which range in apparent molecular weight from 10,000 to 135,000. two of these proteins are glycoproteins and at least four are located on the viral surface. the major lipids are phosphatidyl choline, phosphatidyl ethanolamine, and ... | 1984 | 6740941 |
| dna synthesis in a chlorella-like alga following infection with the virus pbcv-1. | infection of the unicellular, eukaryotic chlorella-like alga nc64a by the large dsdna virus, pbcv-1, resulted in a threefold increase in total dna by 4 hr post infection. viral infection rapidly inhibited host dna synthesis which was followed by the degradation of the host chloroplast and nuclear dna. viral dna synthesis began 30 to 40 min after infection and was dependent on de novo protein synthesis. thus, the virus does not carry all of the components required to form a functional viral dna p ... | 1984 | 18639814 |
| lytic viruses infecting a chlorella-like alga. | a number of viruses which form plaques on the unicellular, eukaryotic, chlorella-like green alga, strain nc64a, were isolated from fresh water ponds and rivers in illinois, north carolina, and south carolina. the viruses were large polyhedrons (160 to 190 nm in diameter) and contained dsdna genomes of ca. 300 kbp. all of the viral dnas hybridized with dna from the previously described pbcv-1 virus. however, the viruses, even many of those isolated from the same water sample, could be distinguish ... | 1985 | 2981448 |
| genetic recombination of the dna plant virus pbcv1 in a chlorella-like alga. | genetic recombination between mutant alleles of a dna plant virus has not previously been observed following infection with intact virions; nor has recombination been observed in any species of the alga chlorella with techniques borrowed from bacteriophage genetics, i isolated temperature-sensitive mutants of the dna virus pbcv1 and showed in three pairwise crosses that they recombined genetically in chlorella at frequencies of approximately 1%. a thorough genetic analysis of a dna plant virus n ... | 1985 | 18640552 |
| restriction endonuclease activity induced by pbcv-1 virus infection of a chlorella-like green alga. | an enzyme was isolated from a eucaryotic, chlorella-like green alga infected with the virus pbcv-1 which exhibits type ii restriction endonuclease activity. the enzyme recognized the sequence gatc and cleaved dna 5' to the g. methylation of deoxyadenosine in the gatc sequence inhibited enzyme activity. in vitro the enzyme cleaved host chlorella nuclear dna but not viral dna because host dna contains gatc and pbcv-1 dna contains gmatc sequences. pbcv-1 dna is probably methylated in vivo by the pb ... | 1986 | 3023890 |
| infection of a chlorella-like alga with the virus pbcv-1: transcriptional studies. | infection of the unicellular, eukaryotic chlorella-like green alga nc64a by the large dsdna containing virus pbcv-1 immediately reduced host rna synthesis. chloroplast rrnas, but not cytosolic rrnas, were degraded following viral infection. northern blot analysis utilizing four cloned fragments of pbcv-1 dna as probes, which represent about 12% of the viral genome, revealed several properties of pbcv-1 transcription: a few viral transcripts were detected within 5 min after infection. each pbcv-1 ... | 1986 | 2417411 |
| replication of the algal virus pbcv-1 in uv-irradiated chlorella. | the large dsdna algal virus, pbcv-1, replicates in uv-irradiated chlorella, albeit more slowly and with a smaller burst size than in untreated chlorella. irradiated cells are unable to form colonies, and endogenous rna and dna synthesis are reduced to background levels. thus a fully function host nucleus is not required for pbcv-1 replication. | 1986 | 3570699 |
| assembly site of the virus pbcv-1 in a chlorella-like green alga: ultrastructural studies. | 1986 | 3750845 | |
| 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 |
| restriction site map of the chlorella virus pbcv-1 genome. | the virus pbcv-1, which replicates in a chlorella-like green alga, has a dsdna genome. the dna was mapped for bamhi, hindiii, and psti restriction sites. the resulting map has a size of 333 kbp and is circular-indicating either covalently closed circular dna or circularly permuted linear dna. several regions of repetitive dna were also identified and located on the restriction map. | 1987 | 24276973 |
| properties of the chlorella receptor for the virus pbcv-1. | the virus pbcv-1 attached rapidly, specifically, and irreversibly to the external surface of cell walls of its host, a unicellular, eukaryotic chlorella-like green alga. attachment was ph and salt dependent. each cell contained at least 5 x 10(4) pbcv-1 binding sites and scatchard analysis indicated that each cell could adsorb 5000 pbcv-1 particles. the pbcv-1 receptor was unaffected by extraction with organic solvents, detergents, high salts, or treatment with several proteases as well as the p ... | 1988 | 3363863 |
| chlorella viruses isolated in china. | plaque-forming viruses of the unicellular, eucaryotic, exsymbiotic, chlorella-like green algae strain nc64a, which are common in the united states, were also present in fresh water collected in the people's republic of china. seven of the chinese viruses were examined in detail and compared with the chlorella viruses previously isolated in the united states. like the american viruses, the chinese viruses were large polyhedra and sensitive to chloroform. they contained numerous structural protein ... | 1988 | 2847652 |
| characterization of dna polymerases in an uninfected and virus pbcv-1-infected green alga--chlorella strain nc64a. | chlorella nc64a cells infected with the large double-stranded dna-containing virus pbcv-1 and uninfected cells were assayed for dna polymerase activity. both uninfected and infected cells contained three forms of dna polymerase activity: (i) an exogenous dna-dependent 10,000 g soluble fraction, (ii) an exogenous dna-dependent 10,000 g particulate fraction, and (iii) a dna-independent 10,000 g particulate fraction. the three dna polymerase activities in the infected and uninfected cells were dist ... | 1989 | 2546899 |
| chlorella viruses contain linear nonpermuted double-stranded dna genomes with covalently closed hairpin ends. | pulsed field electrophoresis established that chlorella viruses contain linear, nonpermuted, 330- to 380-kb dsdna genomes. terminal dna restriction fragments of one virus, pbcv-1, were identified by bal31 exonuclease digestion; the termini probably contain covalently closed hairpin ends. the end fragments cross-hybridize indicating terminal repetition; the region of repetition extends no more than 2.5 kb from the ends. | 1989 | 2916329 |
| 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 |
| 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 |
| characterization of the gene encoding the most abundant in vitro translation product from virus-infected chlorella-like algae. | the gene (33kda) encoding a 33-kda peptide from chlorella virus, pbcv-1, was cloned and sequenced. this gene encodes the most abundant in vitro translation product synthesized from viral mrnas isolated beginning at 20 min post-infection. the message persisted throughout the remainder of the viral life cycle. an open reading frame (orf) of 717 bp, which encodes a polypeptide of 238 amino acids with a predicted m(r) or 26,613, was found on a 2752-bp cloned fragment from pbcv-1 hindiii restriction ... | 1992 | 1339365 |
| chlorella virus pbcv-1 replication is not affected by cytoskeletal disruptors. | the majority, if not the entire life cycle, of the large dsdna-containing algal virus pbcv-1 occurs in localized regions in the cytoplasm. thirteen drugs that disrupt the cytoskeleton had no effect on pbcv-1 replication at concentrations which inhibited host growth. therefore, host cytoskeletal elements do not appear to be important in pbcv-1 morphogenesis. | 1992 | 1568835 |
| characterization of the major capsid protein and cloning of its gene from algal virus pbcv-1. | the major capsid protein (vp54) from chlorella virus pbcv-1 is a glycoprotein and the most abundant viral structural protein. the gene encoding vp54 has been cloned and sequenced. initially, a region of the gene was amplified using the polymerase chain reaction (pcr) primed with oligonucleotides derived from the n-terminal amino acid sequences of purified protein and cyanogen bromide cleavage fragments. the pcr product was used as a probe to map the location of the gene to pbcv-1 genomic pstl re ... | 1992 | 1566573 |
| the dna polymerase gene from chlorella viruses pbcv-1 and ny-2a contains an intron with nuclear splicing sequences. | the deduced amino acid sequences of two eukaryotic chlorella virus (pbcv-1 and ny-2a) dna polymerases are 90% identical and contain amino acid motifs typical of alpha-like (family b) dna polymerases. the open reading frames of both pbcv-1 and ny-2a dna polymerases are interrupted by an identically located, small (101 or 86 nucleotides, respectively) intron that resembles eukaryotic nuclear-spliced messenger rna introns. this discovery suggests that chlorella virus replication has a nuclear phase ... | 1992 | 1585643 |
| evidence for virus-encoded glycosylation specificity. | four spontaneously derived serologically distinct classes of mutants of the paramecium bursaria chlorella virus (pbcv-1) were isolated using polyclonal antiserum prepared against either intact pbcv-1 or pbcv-1-derived serotypes. the oligosaccharide(s) of the viral major capsid protein and two minor glycoproteins determined virus serological specificity. normally, viral glycoproteins arise from host-specific glycosylation of viral proteins; the glycan portion can be altered only by growing the vi ... | 1993 | 7683409 |
| protein glycosylation and myristylation in chlorella virus pbcv-1 and its antigenic variants. | chlorella virus pbcv-1 particles contain three glycoproteins, the major capsid protein vp54 and two minor proteins vp280 and vp260. the major capsid protein is myristylated as well as glycosylated. both modifications are in the carboxyl-terminal portion of the protein. a gene which is modified in a pbcv-1 antiserum-resistant mutant was cloned and sequenced. this gene has an open reading frame of 3099 bases and encodes one of the two large virion glycoproteins (vp260). vp260 contains 13 tandem re ... | 1994 | 8053156 |
| hairpin loop structure at the termini of the chlorella virus pbcv-1 genome. | the termini of the chlorella virus pbcv-1 330-kb dsdna genome consist of 35-nucleotide-long, incompletely base-paired, covalently closed hairpin loops that exist in one of two forms. the two forms are complementary when the 35 nucleotide sequences are inverted with respect to one another (flip and flop). each hairpin loop structure is followed by an identical 2221-bp inverted repeat sequence after which the dna sequence diverges. the strategy for cloning the pbcv-1 dna hairpin ends may be useful ... | 1994 | 8030216 |
| large deletions in antigenic variants of the chlorella virus pbcv-1. | four spontaneously derived, antigenic variants of chlorella virus pbcv-1 contained 27- to 37-kb deletions in the left end of the 330-kb genome. two of the mutants, which were serologically identical, had deletions that began from map position 4.9 or 16 and ended at position 42.2 kb. in total, the two deleted regions encoded 28 putative functional open reading frames (orfs); these deletions probably arose from homologous recombination. the other two mutants, which were serologically identical but ... | 1995 | 8553542 |
| analysis of 43 kb of the chlorella virus pbcv-1 330-kb genome: map positions 45 to 88. | forty-three kb of dna, located at the left end (45 to 88 kb) of the 330-kb chlorella virus pbcv-1 genome, was sequenced and analyzed. eighty-six open reading frames (orfs) 65 codons or longer were identified; 47 were classified as major orfs. these 47 major orfs are densely packed on both strands of pbcv-1 dna. seventeen of these major orfs resemble genes in the sequence databases, including three putative gene products involved in manipulating sugars (glucosamine synthetase, gdp-d-mannose dehyd ... | 1995 | 7676624 |
| photosynthetic shutdown in chlorella nc64a associated with the infection cycle of paramecium bursaria chlorella virus-1. | the effects of the algal virus paramecium bursaria chlorella virus-1 on the photosynthetic physiology of its host, chlorella nc64a, was studied by observing changes in chl fluorescence quenching and o2 exchange. metabolic changes were calibrated against electron microscopic analysis of the morphological changes that occur during the infection cycle. it takes approximately 10 h from attachment of the virus to final lysis of the host cell, so a complete infection cycle can be observed continuously ... | 1995 | 12228553 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| an early gene of the chlorella virus pbcv-1 encodes a functional aspartate transcarbamylase. | pbcv-1 belongs to a family of large viruses that replicate in the exsymbiont green algae chlorella strain nc64a. the viral, 330-kb dna genome encodes a relatively large number of functionally active proteins including restriction and modification enzymes, dna polymerase, glycosylation, and cell wall degrading enzymes. sequencing of the viral dna, now in progress, revealed many major open reading frames (orf), which resemble known genes in sequence data bases and which have not previously been fo ... | 1996 | 8661423 |
| proteolytic processing of chlorella virus cvk2 capsid proteins. | chlorella virus cvk2 particles contain several capsid proteins that are selectively released by treatment with 4 m urea. seven of them (vp52, vp45, vp41, vp25, vp20.5, vp20, and vp16.2) have been identified based on amino acid sequences at the n-terminus. comparison of the amino acid sequences with the corresponding orfs deduced from the nucleotide sequence of pbcv-1, the prototype member of phycodnaviridae, revealed that the cvk2 proteins were processed at the n-terminal region by two different ... | 1997 | 9007082 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| structure of a complex between a cap analogue and mrna guanylyl transferase demonstrates the structural chemistry of rna capping. | paramecium bursaria chlorella virus pbcv-1 mrna guanylyl transferase (capping enzyme) has been complexed with an mrna cap analogue g[5']ppp[5']g and crystallized. the crystals belong to space group c2221 with unit cell dimensions a = 78.4 a, b = 164.1 a, c = 103.3 a, and diffraction data to 3.1 a has been collected by using synchrotron radiation. the structure has been solved by molecular replacement by using each of the two domains in the previously determined structure of the enzyme in complex ... | 1998 | 9465045 |
| chlorella virus dna ligase: nick recognition and mutational analysis. | chlorella virus pbcv-1 dna ligase seals nicked dna substrates consisting of a 5'-phosphate-terminated strand and a 3'-hydroxyl-terminated strand annealed to a bridging dna template strand. the enzyme discriminates at the dna binding step between substrates containing a 5'-phosphate versus a 5'-hydroxyl at the nick. mutational analysis of the active site motif kxdgxr (residues 27-32) illuminates essential roles for the conserved lys, asp and arg moieties at different steps of the ligase reaction. ... | 1998 | 9421510 |
| specificity and fidelity of strand joining by chlorella virus dna ligase. | chlorella virus pbcv-1 dna ligase seals nicked duplex dna substrates consisting of a 5'-phosphate-terminated strand and a 3'-hydroxyl-terminated strand annealed to a bridging template strand, but cannot ligate a nicked duplex composed of two dnas annealed on an rna template. whereas pbcv-1 ligase efficiently joins a 3'-oh rna to a 5'-phosphate dna, it is unable to join a 3'-oh dna to a 5'-phosphate rna. the ligase discriminates at the substrate binding step between nicked duplexes containing 5'- ... | 1998 | 9671815 |
| hyaluronan synthesis in virus pbcv-1-infected chlorella-like green algae. | we previously reported that the chlorella virus pbcv-1 genome encodes an authentic, membrane-associated glycosyltransferase, hyaluronan synthase (has). hyaluronan, a linear polysaccharide chain composed of alternating beta1,4-glucuronic acid and beta1, 3-n-acetylglucosamine groups, is present in vertebrates as well as a few pathogenic bacteria. studies of infected cells show that the transcription of the pbcv-1 has gene begins within 10 min of virus infection and ends at 60-90 min postinfection. ... | 1999 | 10208916 |
| genetic variation of chlorella viruses: variable regions localized on the cvk2 genomic dna. | a physical map of the chlorella virus cvk2 genomic dna has been constructed based on a cosmid contig covering the entire genomic region. by using southern blot analysis with 22 gene probes, the gene arrangement along the genome was compared between cvk2 and pbcv-1, the prototypic member of phycodnaviridae, whose genomic sequence is now available. the major rearrangements were (1) an insertion of a 20-kbp region around the left end of cvk2 dna, (2) a duplication of the gene for major capsid prote ... | 1999 | 10069963 |
| giant viruses infecting algae. | paramecium bursaria chlorella virus (pbcv-1) is the prototype of a family of large, icosahedral, plaque-forming, double-stranded-dna-containing viruses that replicate in certain unicellular, eukaryotic chlorella-like green algae. dna sequence analysis of its 330, 742-bp genome leads to the prediction that this phycodnavirus has 376 protein-encoding genes and 10 transfer rna genes. the predicted gene products of approximately 40% of these genes resemble proteins of known function. the chlorella v ... | 1999 | 10547698 |
| several genes in chlorella virus strain cvg-1 encode putative virion components. | we have started to characterize the capsid components of european chlorella virus isolate cvg-1, a member of the pbi subgroup of the phycodnaviridae. the major coat protein, vp49, was biochemically characterized and the amino acid sequence of the n terminus was determined. subsequently, the corresponding gene was isolated from cvg-1 genomic dna. sequence data were compared to those available from pbcv-1 and other chlorella virus isolates representing the nc64a subgroup of the phycodnaviridae. th ... | 1999 | 10211977 |
| chlorella viruses as a source of novel enzymes. | a special advantage has been conferred upon chlorella cells as tools in biotechnology when viruses (phycodnaviridae) infecting chlorella cells were discovered and isolated. the viruses are large icosahedral particles (150-200 nm in diameter), containing a giant, 330-380 kbp long, linear dsdna genome. recently, the nucleotide sequence of the 330,740-bp genome of pbcv-1, the prototype virus of phycodnaviridae, was determined, and up to 702 open reading frames (orfs) were identified along the genom ... | 1999 | 16232628 |
| 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 |
| 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 |
| 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 |
| 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 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| molecular and genetic evidence for a virus-encoded glycosyltransferase involved in protein glycosylation. | the major capsid protein, vp54, of chlorella virus pbcv-1 is a glycoprotein that contains either one glycan of approximately 30 sugar residues or two similar glycans of approximately 15 residues. previous analysis of pbcv-1 antigenic mutants that contained altered vp54 glycans led to the conclusion that unlike other glycoprotein-containing viruses, most, if not all, of the enzymes involved in the synthesis of the vp54 glycan are probably encoded by pbcv-1 (i.-n. wang et al., 1993, proc. natl. ac ... | 2001 | 11437667 |
| voltage-dependence of virus-encoded miniature k+ channel kcv. | kcv is a k+-selective channel encoded by the paramecium bursaria chlorella virus 1 (pbvc-1). expression of this protein, so far the smallest known functional k+ channel, in xenopus oocytes reveals an instantaneous and a time-dependent component during voltage-clamp steps. these two components have an identical sensitivity to the inhibitor amantadine, implying that they reflect distinct kinetic features of the same channel. about 70% of the channels are always open; at hyperpolarizing voltages th ... | 2002 | 12029374 |
| [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 |
| isolation and characterization of chlorella viruses from freshwater sources in korea. | we isolated 23 chlorella viruses from 9 korean cities. the viruses were initially amplified in the chlorella strain nc64a. pure isolates were obtained by repeated plaque isolations. a sds-page analysis revealed similar but distinct protein patterns, both among the group of purified viruses and in comparison with the prototype chlorella virus pbcv-1. digestions of the 330- to 350-kb genomic dnas with 10 restriction enzymes revealed different restriction fragment patterns among the isolates. one i ... | 2002 | 12442887 |
| chitin synthesis in chlorovirus cvk2-infected chlorella cells. | hyaluronan synthesis in chlorovirus pbcv-1-infected chlorella cells was previously reported (deangelis et al., 1997). in contrast, we report here on the detection, characterization, and expression of a gene for chitin synthase (chs) encoded by chlorovirus cvk2 isolated in kyoto, japan. the cvk2 chs gene encoding an open reading frame of 516 aa was expressed as early as 10 min postinfection (p.i.), peaked at 20-40 min p.i., and disappeared at 120-180 min p.i. the chitin polysaccharide began to ac ... | 2002 | 12429521 |
| 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 |
| 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 |
| 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 |
| 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 |
| possible function for virus encoded k+ channel kcv in the replication of chlorella virus pbcv-1. | the k+ channel kcv is encoded by the chlorella virus pbcv-1. there is evidence that this channel plays an essential role in the replication of the virus, because both pbcv-1 plaque formation and kcv channel activity in xenopus oocytes have similar sensitivities to inhibitors. here we report circumstantial evidence that the kcv channel is important during virus infection. recordings of membrane voltage in the host cells chlorella nc64a reveal a membrane depolarization within the first few minutes ... | 2003 | 12972144 |
| unusual life style of giant chlorella viruses. | paramecium bursaria chlorella virus (pbcv-1) is the prototype of a family of large, icosahedral, plaque-forming, dsdna viruses that replicate in certain unicellular, eukaryotic chlorella-like green algae. its 330-kb genome contains approximately 373 protein-encoding genes and 11 trna genes. the predicted gene products of approximately 50% of these genes resemble proteins of known function, including many that are unexpected for a virus, e.g., ornithine decarboxylase, hyaluronan synthase, gdp-d-m ... | 2003 | 14616059 |
| the viral potassium channel kcv: structural and functional features. | the chlorella virus pbcv-1 was the first virus found to encode a functional potassium channel protein (kcv). kcv is small (94 aa) and basically consists of the m1-p-m2 (membrane-pore-membrane) module typical of the pore regions of all known potassium channels. kcv forms functional channels in three heterologous systems. this brief review discusses the gating, permeability and modulation properties of kcv and compares them to the properties of bacterial and mammalian k+ channels. | 2003 | 12972145 |
| genetic diversity in chlorella viruses flanking kcv, a gene that encodes a potassium ion channel protein. | the chlorella virus pbcv-1 encodes a 94-amino acid protein named kcv that produces a k+-selective and slightly voltage-sensitive conductance when expressed in heterologous systems. as reported herein, (i) northern analysis of kcv expression in pbcv-1-infected cells revealed a complicated pattern suggesting that the gene might be transcribed as a di- or tri-cistronic mrna both at early and late times after virus infection. (ii) the protein kinase inhibitors h-89, a3, and staurosporine inhibited p ... | 2004 | 15262503 |
| long distance interactions within the potassium channel pore are revealed by molecular diversity of viral proteins. | kcv is a 94-amino acid protein encoded by chlorella virus pbcv-1 that corresponds to the pore module of k(+) channels. therefore, kcv can be a model for studying the protein design of k(+) channel pores. we analyzed the molecular diversity generated by approximately 1 billion years of evolution on kcv genes isolated from 40 additional chlorella viruses. because the channel is apparently required for virus replication, the kcv variants are all functional and contain multiple and dispersed substit ... | 2004 | 15105432 |
| small potassium ion channel proteins encoded by chlorella viruses. | kcv, a 94-aa protein encoded by paramecium bursaria chlorella virus 1, is the smallest known protein to form a functional potassium ion channel and basically corresponds to the "pore module" of potassium channels. both viral replication and channel activity are inhibited by the ion channel blockers barium and amantadine but not by cesium. genes encoding kcv-like proteins were isolated from 40 additional chlorella viruses. differences in 16 of the 94 amino acids were detected, producing six kcv-l ... | 2004 | 14762169 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| isolation and characterization of a new type of chlorovirus that infects an endosymbiotic chlorella strain of the heliozoon acanthocystis turfacea. | a novel virus, named acanthocystis turfacea chlorella virus (atcv), that infects endosymbiotic chlorella algae of the heliozoon acanthocystis turfacea was isolated from freshwater samples. electron microscopic analysis of atcv revealed that the viral capsid has a distinct icosahedral shape with a diameter of 140-190 nm. filamentous structures extending from some of the virus vertices, which may aid attachment of the virus to host cells, were also observed. the capsid is made up of one major coat ... | 2005 | 16186243 |
| chlorovirus: a genus of phycodnaviridae that infects certain chlorella-like green algae. | summary taxonomy: chlorella viruses are assigned to the family phycodnaviridae, genus chlorovirus, and are divided into three species: chlorella nc64a viruses, chlorella pbi viruses and hydra viridis chlorella viruses. chlorella viruses are large, icosahedral, plaque-forming, dsdna viruses that infect certain unicellular, chlorella-like green algae. the type member is paramecium bursaria chlorella virus 1 (pbcv-1). physical properties: chlorella virus particles are large (molecular weight approx ... | 2005 | 20565652 |