| a medium for the axenic culture of chlorella-bearing paramecium bursaria in the light. | | 1975 | 1114583 |
| photoreception of paramecium cilia: localization of photosensitivity and binding with anti-frog-rhodopsin igg. | paramecium bursaria is photosensitive and accumulates in a lighted area. the cells can be deciliated by a brief suspension in dilute ethanol. both intact and deciliated cells showed depolarization in response to light stimulation by a step-increase from dark to above 0.7 mw cm-2 (550 nm). on the other hand, after a step-increase to below 0.4 mw cm-1, intact cells showed hyperpolarization, while the deciliated cells showed no change in membrane potential. this difference in membrane potential res ... | 1991 | 1757502 |
| the utilization of bacteria as food for paramecium bursaria. | | 1973 | 4199960 |
| dna amounts in the nuclei of paramecium bursaria. | | 1973 | 4682088 |
| infection of alga-free paramecium bursaria with strains of chlorella, scenedesmus, and a yeast. | | 1965 | 5859658 |
| comparative freeze-fracture study of perialgal and digestive vacuoles in paramecium bursaria. | in the endosymbiotic unit of paramecium bursaria (ciliata) and chlorella sp. (chlorophyceae) algae are enclosed individually in perialgal vacuoles, which do not show acid phosphatase activity and thus differ from digestive vacuoles. both types of vacuoles have been studied by freeze-fracture. perialgal vacuoles are nearly spherical; their membrane always fits tightly to the algal surface. the vacuole size and shape do not vary much. during division of the algal cell into four autospores the vacu ... | 1984 | 6520143 |
| [clinical and kinetic characteristics of a temporarily nonproliferating subpopulation of bone marrow blast cells from acute leukemia patients (based on data on dna autoradiography and cytophotometry]. | the morphology of paramecium bursaria cells, both originally possessing 2 micronuclei (mi), or one mi, has been studied after a local uv irradiation of the germ nuclei. elimination of one of the mi in bimicronuclear cells usually did not lead to general cytological damage in the uv progeny. irradiation of mi in the unimicronuclear cells resulted in the following: producing of amicronuclear (mi-) uv subclones, 86% of which appeared to be non-viable. the mi- cells are characterized by the appearan ... | 1983 | 6679426 |
| infections of paramecium bursaria with bacteria and yeasts. | infections of paramecium bursaria with bacteria and yeasts are reported. bacteria and yeasts multiply in the algae-free ciliate and are transmitted at various conditions as are symbiotic chlorellae. like chlorellae, the bacteria and the yeast cells are situated in perisymbiont vacuoles. both bacteria and yeasts maintain their capability for independent existence and can be grown on standard nutrient agar. infection experiments show that aposymbiotic p. bursaria can be infected with chlorella, ba ... | 1982 | 7183698 |
| participation of gtp-binding protein in the photo-transduction of paramecium bursaria. | analysis of the flow of light information in paramecium, especially the participation of gtp-binding protein, was carried out. injection of gdp-beta-s into paramecium cell abolished the light-induced inward current. the partially purified rhodopsin-like protein (rlp) that we obtained activated frog rod outer segments (ros) gtpase. a gtp-binding protein, with mw 57,000 was detected by immunostaining with anti-rat g alpha rabbit igg. these results suggest that the light information flows from the ... | 1996 | 9078404 |
| is the major capsid protein of iridoviruses a suitable target for the study of viral evolution? | iridoviruses are large cytoplasmic dna viruses that are specific for different insect or vertebrate hosts. the major structural component of the non-enveloped icosahedral virus particles is the major capsid protein (mcp) which appears to be highly conserved among members of the family iridoviridae, phycodnaviridae, and african swine fever virus. the amino acid sequences of the known mcps were used in comparative analyses to elucidate the phylogenic relationships between different cytoplasmic dna ... | 1998 | 9562891 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| [analysis of natural diversity of symbiotic relationships in the paramecium bursaria--holospora curviuscula system]. | bacteria of the genus holospora belong to obligatory endonucleobionts of ciliates of the genus paramecium. the bacteria show specificity towards the particular host species and the types of nuclei they infect: macro- or micronuclei. during a long-term screening of p. bursaria clones, belonging to three different syngens, holospora inhibited cells of two syngens only. using the number of host clones and symbiont isolates, it was shown that h. curviuscula was unable to pass successfully through th ... | 2001 | 11517669 |
| 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 |
| [effect of symbiotic algae on the photoaccumulation capacity of cells of the ciliate paramecium bursaria]. | the character of the effect produced by symbiotic algae on photodependent behavior of their host ciliates, paramecium bursaria, was determined. partially alga-freed paramecia showed a reliable increase in the rates of photoaccumulation. the photoaccumulation rate gradually decreased with a further decrease in the number of zoochlorellae. once the chlorophyll content fell down to 20-25 mu/l, the ciliates lost their capacity for photoaccululation. a mathematical model of photoaccumulation has been ... | 2002 | 12094770 |
| 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 |
| ca2+-dependent contractility of isolated and demembranated macronuclei in the hypotrichous ciliate euplotes aediculatus. | the hypotrichous ciliated protozoan euplotes aediculatus possesses a characteristic c-shaped somatic nucleus (macronucleus) within the cytoplasm, which shows dynamic shape change during the cell cycle. it is shown that isolated macronuclei possess ca(2+)-dependent contractility. macronuclei were isolated, stuck fast on the glass surface, and subjected to different concentrations of ca(2+) in a ca(2+)-egta buffer. the nuclei became expanded at [ca(2+)]<10(-7)m, and they contracted on subsequent a ... | 2003 | 12531187 |
| 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 |
| the acute toxicity of nickel to freshwater ciliates. | the acute toxicity of nickel to 12 species of freshwater ciliates was examined in laboratory tests. after exposing standard cultures of the ciliates to a soluble compound of nickel (nicl(2).6h(2)o) at several selected concentrations close to the lethal limit for 24 h, the mortality rate was registered and the lc(50) values (with 95% confidence intervals) were calculated. large differences appeared in sensitivities of the 12 species to the metal. ciliated protozoa such as spirostomum teres (0.17 ... | 2000 | 15092912 |
| 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 |
| 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 |
| a new approach for the assessment of acrylamide toxicity using a green paramecium. | exposure to acrylamide induces neurotoxic effects in humans. in addition, it induces genotoxic, reproductive and carcinogenic effects in laboratory animals. however, no convenient bioassay system for assessing acrylamide toxicity to animal and plant cells has been proposed to date. the present study aims to evaluate acrylamide toxicity to a green paramecium, paramecium bursaria, bearing many endosymbiotic algae, because some chemicals are highly toxic to paramecia or microalgae, and some protozo ... | 2005 | 15582361 |
| 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 |
| symbiotic chlorella sp. of the ciliate paramecium bursaria do not prevent acidification and lysosomal fusion of host digestive vacuoles during infection. | each symbiotic chlorella sp. of the ciliate paramecium bursaria is enclosed in a perialgal vacuole derived from the host digestive vacuole, and thereby the alga is protected from digestion by lysosomal fusion. algae-free cells can be reinfected with algae isolated from algae-bearing cells by ingestion into digestive vacuoles. to examine the timing of acidification and lysosomal fusion of the digestive vacuoles and of algal escape from the digestive vacuole, algae-free cells were mixed with isola ... | 2005 | 15997335 |
| 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 |
| photoadaptation alters the ingestion rate of paramecium bursaria, a mixotrophic ciliate. | bacteriovorous protozoa harboring symbiotic algae are abundant in aquatic ecosystems, yet despite a recent interest in protozoan bacterivory, the influence of light on their ingestion rates has not been investigated. in this study, paramecium bursaria containing endosymbiotic chlorella was tested for the effect of light on its ingestion rate. p. bursaria was grown for 4 to 6 days under five different light fluxes ranging from 1 to 90 microeinsteins s m. ingestion rates were determined by using 0 ... | 1991 | 16348540 |
| structure of an archaeal virus capsid protein reveals a common ancestry to eukaryotic and bacterial viruses. | archaea and their viruses are poorly understood when compared with the eukarya and bacteria domains of life. we report here the crystal structure of the major capsid protein (mcp) of the sulfolobus turreted icosahedral virus, an archaeal virus isolated from an acidic hot spring (ph 2-4, 72-92 degrees c) in yellowstone national park. the structure is nearly identical to the mcp structures of the eukaryotic paramecium bursaria chlorella virus, and the bacteriophage prd1, and shows a common fold wi ... | 2005 | 16357204 |
| mycosporines from freshwater yeasts: a trophic cul-de-sac? | mycosporine-like amino-acids (maas) are found in aquatic bacteria, algae, and animals. a related compound, the mycosporine-glutaminol-glucoside (myc-glu-glu), has recently been reported in freshwater yeasts. although animals depend on other organisms as their source of maas, they can efficiently accumulate them in their tissues. in this work we assessed the potential transfer of the yeast mycosporine myc-glu-glu from the diet into the copepod boeckella antiqua and the ciliate paramecium bursaria ... | 2006 | 16395424 |
| a model-based parallel origin and orientation refinement algorithm for cryotem and its application to the study of virus structures. | we present a model-based parallel algorithm for origin and orientation refinement for 3d reconstruction in cryotem. the algorithm is based upon the projection theorem of the fourier transform. rather than projecting the current 3d model and searching for the best match between an experimental view and the calculated projections, the algorithm computes the discrete fourier transform (dft) of each projection and searches for the central section ("cut") of the 3d dft that best matches the dft of th ... | 2006 | 16459100 |
| 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 |
| 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 |
| toxicity of the quinalphos metabolite 2-hydroxyquinoxaline: growth inhibition, induction of oxidative stress, and genotoxicity in test organisms. | the quinalphos metabolite 2-hydroxyquinoxaline (hqo), previously shown to photocatalytically destroy antioxidant vitamins and biogenic amines in vitro, was tested for toxicity in several small aquatic organisms and for mutagenicity in salmonella typhimurium. in the rotifer philodina acuticornis, hqo caused the disappearance of large individuals and increased hydroperoxide concentration. the latter effect was not only observed in animals kept in a light/dark cycle, but also in constant darkness, ... | 2007 | 17295279 |
| an experimental test of the symbiosis specificity between the ciliate paramecium bursaria and strains of the unicellular green alga chlorella. | the ciliate paramecium bursaria living in mutualistic relationship with the unicellular green alga chlorella is known to be easily infected by various potential symbionts/parasites such as bacteria, yeasts and other algae. permanent symbiosis, however, seems to be restricted to chlorella taxa. to test the specificity of this association, we designed infection experiments with two aposymbiotic p. bursaria strains and chlorella symbionts isolated from four paramecium strains, seven other ciliate h ... | 2007 | 17635555 |
| photo-oxidative stress in symbiotic and aposymbiotic strains of the ciliate paramecium bursaria. | we tested the hypothesis that photo-oxidative stress is greater in symbiotic representatives of the freshwater ciliate paramecium bursaria than in aposymbiotic (i.e., without chlorella) ones. the level of oxidative stress was determined by assessing reactive oxygen species (ros) with two fluorescent probes (hydroethidine and dihydrorhodamine123) by flow cytometry in exponential and stationary growth phases of both strains. photo-oxidative stress was assessed in the laboratory after exposure of t ... | 2007 | 17668113 |
| the structure of a putative scaffolding protein of immature poxvirus particles as determined by electron microscopy suggests similarity with capsid proteins of large icosahedral dna viruses. | orf virus, the prototype parapoxvirus, is responsible for contagious ecthyma in sheep and goats. the central region of the viral genome codes for proteins highly conserved among vertebrate poxviruses and which are frequently essential for viral proliferation. analysis of the recently published genome sequence of orf virus revealed that among such essential proteins, the protein orfv075 is an orthologue of d13, the rifampin resistance gene product critical for vaccinia virus morphogenesis. previo ... | 2007 | 17670837 |
| 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 |
| one-base excess adaptor ligation method for walking uncloned genomic dna. | this report describes a novel and efficient method for walking the sequence of a genomic deoxyribonucleic acid (dna) from a known region to an unknown region based on an oligodeoxynucleotide (oligo) cassette-mediated polymerase chain reaction technique. in this method, genomic dna is digested by a restriction enzyme that generates a sticky 5'-end, followed by ligation of a one-base excess oligo-adaptor using t4 dna ligase. the adaptor consists of two complementary oligos that form the same stick ... | 2008 | 18071644 |
| 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 |
| [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 |
| symbiotic ciliates receive protection against uv damage from their algae: a test with paramecium bursaria and chlorella. | we assessed the photoprotective role of symbiotic chlorella in the ciliate paramecium bursaria by comparing their sensitivity to uv radiation (uvr) with chlorella-reduced and chlorella-free (aposymbiotic) cell lines of the same species. aposymbiotic p. bursaria had significantly higher mortality than the symbiotic cell lines when exposed to uvr. to elucidate the protection mechanism, we assessed the algal distribution within the ciliate using thin-sections and transmission electron microscopy an ... | 2009 | 19195930 |
| 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 |
| phylogenetically close group i introns with different positions among paramecium bursaria photobionts imply a primitive stage of intron diversification. | group i introns are a distinct rna group that catalyze their excision from precursor rna transcripts and ligate the exons. group i introns have a sporadic and highly biased distribution due to the two intron transfer mechanisms of homing and reverse splicing. these transfer pathways recognize assigned sequences even when introns are transferred beyond the species level. consequently, introns at homologous gene sites between different host organisms are more related than those at heterologous sit ... | 2009 | 19279084 |
| 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 |
| a new laboratory cultivation of paramecium bursaria using non-pathogenic bacteria strains. | in most studies dealing with the laboratory cultivation of paramecia (paramecium bursaria), klebsiella pneumoniae bacteria are used to inoculate the medium. however, klebsiella pneumoniae is a typical pathogen, and its use is always associated with a risk of infection. the aim of the present research was to examine non-pathogenic bacteria strains as components of the medium for paramecium bursaria. the paramecia were incubated on lettuce infusions bacterized with different bacteria strains: baci ... | 2010 | 20737917 |
| the systematics of zoochlorella revisited employing an integrative approach. | symbiosis of green algae with protozoa and invertebrates has been studied for more than 100 years. endosymbiotic green algae are widely distributed in ciliates (e.g. paramecium, stentor, climacostomum, coleps, euplotes), heliozoa (e.g. acanthocystis) and invertebrates (e.g. hydra, spongilla), and have traditionally been identified as named or unnamed species of chlorella beij. or zoochlorella k. brandt or referred to as chlorella-like algae or zoochlorellae. we studied 17 strains of endosymbiont ... | 2010 | 20874732 |
| a green paramecium strain with abnormal growth of symbiotic algae. | some hundred cells of chlorella-like green algae are naturally enclosed within the cytoplasm of a single cell of green paramecia (paramecium bursaria). therefore, p. bursaria serves as an experimental model for studying the nature of endo-symbiosis made up through chemical communication between the symbiotic partners. for studying the mechanism of symbiotic regulations, the materials showing successful symbiosis are widely used. apart from such successful model materials, some models for symbiot ... | 2010 | 21319710 |
| forced symbiosis between synechocystis spp. pcc 6803 and apo-symbiotic paramecium bursaria as an experimental model for evolutionary emergence of primitive photosynthetic eukaryotes. | single-cell green paramecia (paramecium bursaria) is a swimming vehicle that carries several hundred cells of endo-symbiotic green algae. here, a novel model for endo-symbiosis, prepared by introducing and maintaining the cells of cyanobacterium (synechocystis spp. pcc 6803) in the apo-symbiotic cells of p. bursaria is described. | 2011 | 21494093 |
| association of paramecium bursaria chlorella viruses with paramecium bursaria cells: ultrastructural studies. | paramecium bursaria chlorella viruses were observed by applying transmission electron microscopy in the native symbiotic system paramecium bursaria (ciliophora, oligohymenophorea) and the green algae chlorella (chlorellaceae, trebouxiophyceae). virus particles were abundant and localized in the ciliary pits of the cortex and in the buccal cavity of p. bursaria. this was shown for two types of the symbiotic systems associated with two types of chlorella viruses - pbi or nc64a. a novel quantitativ ... | 2011 | 21700436 |
| [In Process Citation]. | | 2011 | 22168016 |
| 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 |
| interactions between paramecium bursaria (protozoa, ciliophora, hymenostomatida) and their nuclear symbionts: i. phenomenon of symbiogenic lysis of the bacterium holospora acuminata. | in experimental infections the phenomenon of the lysis of symbiotic bacteria (sb) in the host-cell nucleus was discovered for the first time. light optical investigations were made of 308 possible combinations of experimental infections of 44 clones of originally symbiont-free paramecium bursaria by 7 strains of sb holospora acuminata of different origin. in 5% of the cases studied the early stages of infection appeared to be the same as in susceptible strains, but all the sb were lysed during 1 ... | 2011 | 23195446 |
| infection of algae-free paramecium bursaria with symbiotic chlorella sp. isolated from green paramecia: i. effect of the incubation period. | the significance of the length of incubation (30 sec to 48 h) of algae-free paramecium bursaria with symbiotic chlorella sp. for the success of infection, i.e. the reestablishment of the endosymbiotic algae has been investigated. when algae are brought together with paramecia, they are rapidly taken up by the ciliates. during a 30 sec incubation one ciliate engulfs about 50 chlorellae. a prolongation of the incubation period increases the number of ingested algae. however, the success of infecti ... | 2011 | 23195469 |
| synchronous induction of detachment and reattachment of symbiotic chlorella spp. from the cell cortex of the host paramecium bursaria. | paramecium bursaria harbor several hundred symbiotic chlorella spp. each alga is enclosed in a perialgal vacuole membrane, which can attach to the host cell cortex. how the perialgal vacuole attaches beneath the host cell cortex remains unknown. high-speed centrifugation (> 1000×g) for 1min induces rapid detachment of the algae from the host cell cortex and concentrates the algae to the posterior half of the host cell. simultaneously, most of the host acidosomes and lysosomes accumulate in the a ... | 2013 | 23912150 |
| 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 |
| arrest of cytoplasmic streaming induces algal proliferation in green paramecia. | a green ciliate paramecium bursaria, bearing several hundreds of endosymbiotic algae, demonstrates rotational microtubule-based cytoplasmic streaming, in which cytoplasmic granules and endosymbiotic algae flow in a constant direction. however, its physiological significance is still unknown. we investigated physiological roles of cytoplasmic streaming in p. bursaria through host cell cycle using video-microscopy. here, we found that cytoplasmic streaming was arrested in dividing green paramecia ... | 2007 | 18159235 |
| 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 |
| micro-particle transporting system using galvanotactically stimulated apo-symbiotic cells of paramecium bursaria. | it is well known that paramecium species including green paramecia (paramecium bursaria) migrate towards the anode when exposed to an electric field in a medium. this type of a cellular movement is known as galvanotaxis. our previous study revealed that an electric stimulus given to p bursaria is converted to a galvanotactic cellular movement by involvement of t-type calcium channel on the plasma membrane [aonuma et al. (2007), z. naturforsch. 62c, 93-102]. this phenomenon has attracted the atte ... | 2010 | 19678550 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| prolonged synthesis of hyaluronan by chlorella cells infected with chloroviruses. | hyaluronan (ha) synthesis by microalgal chlorella cells in combination with chloroviruses represents a unique eco-friendly process for converting solar energy and co2 into useful materials. however, at the final stage of viral infection, infected host cells are completely lysed, and thus ha should be harvested before cell lysis. in the current study, two methods were investigated to improve the yield of ha: (i) adopting slow-growing chlorovirus isolates and (ii) modification of the virus replica ... | 2013 | 23273909 |
| paramecium bursaria chlorella virus 1 proteome reveals novel architectural and regulatory features of a giant virus. | the 331-kbp chlorovirus paramecium bursaria chlorella virus 1 (pbcv-1) genome was resequenced and annotated to correct errors in the original 15-year-old sequence; 40 codons was considered the minimum protein size of an open reading frame. pbcv-1 has 416 predicted protein-encoding sequences and 11 trnas. a proteome analysis was also conducted on highly purified pbcv-1 virions using two mass spectrometry-based protocols. the mass spectrometry-derived data were compared to pbcv-1 and its host chlo ... | 2012 | 22696644 |
| 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 |
| 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 |
| 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 |
| 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 |
| revised mimivirus major capsid protein sequence reveals intron-containing gene structure and extra domain. | acanthamoebae polyphaga mimivirus (apm) is the largest known dsdna virus. the viral particle has a nearly icosahedral structure with an internal capsid shell surrounded with a dense layer of fibrils. a capsid protein sequence, d13l, was deduced from the apm l425 coding gene and was shown to be the most abundant protein found within the viral particle. however this protein remained poorly characterised until now. a revised protein sequence deposited in a database suggested an additional n-termina ... | 2009 | 19432951 |
| epigenetic transcriptional repression of cellular genes by a viral set protein. | viruses recruit host proteins to secure viral genome maintenance and replication. however, whether they modify host histones directly to interfere with chromatin-based transcription is unknown. here we report that paramecium bursaria chlorella virus 1 (pbcv-1) encodes a functional set domain histone lys methyltransferase (hkmtase) termed vset, which is linked to rapid inhibition of host transcription after viral infection. we show that vset is packaged in the pbcv-1 virion, and that it contains ... | 2008 | 19160493 |
| the a312l 5'-utr of chlorella virus pbcv-1 is a translational enhancer in arabidopsis thaliana. | pbcv-1 (paramecium bursaria chlorella virus) is a large double stranded dna virus that replicates in certain eukaryotic chlorella like green algae. the pbcv-1 a312l gene encodes a 33-kda protein whose function currently is unknown. the 5'-utr of the a312l mrna is 153 nucleotides, longer than the 5'-utr in any other pbcv-1 gene. the sequence 5'-aaac was repeated 17 times within 156bp 5' to the a312l gene start codon and this sequence was repeated 13 times continuously in the 5'-utr of the mrna. r ... | 2009 | 19118587 |
| kinetic and thermodynamic characterization of the rna guanylyltransferase reaction. | an rna guanylyltransferase activity is involved in the synthesis of the cap structure found at the 5' end of eukaryotic mrnas. the rna guanylyltransferase activity is a two-step ping-pong reaction in which the enzyme first reacts with gtp to produce the enzyme-gmp covalent intermediate with the concomitant release of pyrophosphate. in the second step of the reaction, the gmp moiety is then transferred to a diphosphorylated rna. both reactions were previously shown to be reversible. in this study ... | 2008 | 18298088 |
| chlorella viruses. | chlorella viruses or chloroviruses are large, icosahedral, plaque-forming, double-stranded-dna-containing viruses that replicate in certain strains of the unicellular green alga chlorella. dna sequence analysis of the 330-kbp genome of paramecium bursaria chlorella virus 1 (pbcv-1), the prototype of this virus family (phycodnaviridae), predict approximately 366 protein-encoding genes and 11 trna genes. the predicted gene products of approximately 50% of these genes resemble proteins of known fun ... | 2006 | 16877063 |
| virion-associated restriction endonucleases of chloroviruses. | chloroviruses are large, double-stranded-dna, plaque-forming viruses that infect certain eukaryotic chlorella-like green algae. the prototype of the genus is paramecium bursaria chlorella virus 1 (pbcv-1). chlorovirus genomes contain various amounts of methylated nucleotides due to virus-encoded dna methyltransferases (mtases); about 25% of the mtases are associated with companion dna site-specific (restriction) endonucleases (reases). these enzymes constitute virally encoded restriction-modific ... | 2006 | 16873267 |
| catalytic mechanism and structure of viral flavin-dependent thymidylate synthase thyx. | by using biochemical and structural analyses, we have investigated the catalytic mechanism of the recently discovered flavin-dependent thymidylate synthase thyx from paramecium bursaria chlorella virus-1 (pbcv-1). site-directed mutagenesis experiments have identified several residues implicated in either nadph oxidation or deprotonation activity of pbcv-1 thyx. chemical modification by diethyl pyrocarbonate and mass spectroscopic analyses identified a histidine residue (his53) crucial for nadph ... | 2006 | 16707489 |
| structural insights of the specificity and catalysis of a viral histone h3 lysine 27 methyltransferase. | set domain lysine methyltransferases are known to catalyze site and state-specific methylation of lysine residues in histones that is fundamental in epigenetic regulation of gene activation and silencing in eukaryotic organisms. here we report the three-dimensional solution structure of the set domain histone lysine methyltransferase (vset) from paramecium bursaria chlorella virus 1 bound to cofactor s-adenosyl-l-homocysteine and a histone h3 peptide containing mono-methylated lysine 27. the dim ... | 2006 | 16603186 |
| 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 |
| 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 |