Biomedical subjects

Hideki Onimatsu

Publications and source records attributed to Hideki Onimatsu.

4 recordsLinked to original sources

PubMed2006

C-terminal repetitive motifs in Vp130 present at the unique vertex of the Chlorovirus capsid are essential for binding to the host Chlorella cell wall.

Previously, Vp130, a chloroviral structural protein, was found to have host-cell-wall-binding activity for NC64A-viruses (PBCV-1 and CVK2). In this study, we have isolated and characterized the corresponding protein from chlorovirus CVGW1, one of Pbi-viruses that have a different host range. In NC64A-viruses, Vp130 consists of a highly conserved N-terminal domain, internal repeats of 70-73 aa motifs and a C-terminal domain occupied by 23-26 tandem repeats of a PAPK motif. However, CVGW1 was found to have a slightly different Vp130 construction where the PAPK repeats were not in the C-terminus but internal. Immunofluorescence microscopy with a specific antibody revealed that the C-terminal region containing the Vp130 repetitive motifs from PBCV-1 and CVK2 was responsible for binding to Chlorella cell walls. Furthermore, by immunoelectron microscopy and immunofluorescence microscopy, Vp130 was localized at a unique vertex of the chlorovirus particle and was found to be masked through binding to the host cells. These results suggested that Vp130 is localized at a unique vertex on the virion, with the C-terminal repetitive units outside for cell wall binding.

Amino Acid Sequence↗

PubMed2006

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 function, including many that are completely unexpected for a virus. In addition, the chlorella viruses have several features and encode many gene products that distinguish them from most viruses. These products include: (1) multiple DNA methyltransferases and DNA site-specific endonucleases, (2) the enzymes required to glycosylate their proteins and synthesize polysaccharides such as hyaluronan and chitin, (3) a virus-encoded K(+) channel (called Kcv) located in the internal membrane of the virions, (4) a SET domain containing protein (referred to as vSET) that dimethylates Lys27 in histone 3, and (5) PBCV-1 has three types of introns; a self-splicing intron, a spliceosomal processed intron, and a small tRNA intron. Accumulating evidence indicates that the chlorella viruses have a very long evolutionary history. This review mainly deals with research on the virion structure, genome rearrangements, gene expression, cell wall degradation, polysaccharide synthesis, and evolution of PBCV-1 as well as other related viruses.

Base Sequence↗

PubMed2004

vAL-1, a novel polysaccharide lyase encoded by chlorovirus CVK2.

Cell wall materials isolated from Chlorella cells were degraded by the polysaccharide-degrading enzyme vAL-1 encoded by chlorovirus CVK2. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analyses of the degradation products (oligosaccharides) revealed major oligosaccharides contain unsaturated GlcA at the reducing terminus, and a side chain attached at C2 or C3 of GlcA(C4?C5), which mainly consisted of Ara, GlcNAc and Gal. The results indicated that vAL-1 is a novel polysaccharide lyase, cleaving chains of beta- or alpha-1,4-linked GlcAs. The unique structures of Chlorella cell wall were also revealed. Studies on the complicated structures of naturally occurring polysaccharides will be greatly facilitated by using vAL-1 as a tool in structural analysis.

Cell Wall↗

PubMed2004

Vp130, a chloroviral surface protein that interacts with the host Chlorella cell wall.

A protein, Vp130, that interacts with the host cell wall was isolated from Chlorovirus CVK2. From its peptide sequence, the gene for Vp130 was identified on the PBCV-1 genomic sequence as an ORF combining A140R and A145R. In Vp130, the N-terminus was somehow modified and the C-terminus was occupied by 23-26 tandem repeats of a PAPK motif. In the internal region, Vp130 contained seven repeats of 70-73 amino acids, each copy of which was separated by PAPK sequences. This protein was well conserved among NC64A viruses. A recombinant rVp130N protein formed in Escherichia coli was shown not only to bind directly to the host cell wall in vitro but also to specifically bind to the host cells, as demonstrated by fluorescence microscopy. Because externally added rVp130N competed with CVK2 to bind to host cells, Vp130 is most likely to be a host-recognizing protein on the virion.

Amino Acid Sequence↗