\u3ci\u3eParamecium bursaria\u3c/i\u3e Chlorella Virus 1 Proteome Reveals Novel Architectural and Regulatory Features of a Giant Virus

摘要

The 331 kilobase pairs chlorovirus PBCV-1 genome was re-sequenced and annotated to correct errors in the original 15 year old sequence; forty codons was considered the minimum protein size of an open reading frame. PBCV-1 encodes 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 Chlorella variabilis NC64A predicted proteomes. Combined, these analyses revealed 148 unique virus-encoded proteins associated with the virion (about 35% of the coding capacity of the virus) and one host protein. Some of these proteins appear to be structural/architectural, whereas others have enzymatic, chromatin modification and signal transduction functions. Most (106) of these proteins have no known function or homologs in the existing gene databases except as orthologs with other chloroviruses, phycodnaviruses and nuclear-cytoplasmic large DNA viruses. The genes encoding these proteins are dispersed throughout the virus genome and most are transcribed late or early late in the infection cycle, which is consistent with virion morphogenesis.