Leary T P, Desai S M, Erker J C, Mushahwar I K
Virus Discovery Group, Abbott Laboratories, Dept., North Chicago, IL 60064, USA.
J Gen Virol. 1997 Sep;78 ( Pt 9):2307-13. doi: 10.1099/0022-1317-78-9-2307.
Recently, gene fragments of several novel variants of GB virus A were isolated from the serum of distinct monkey species that had not been experimentally inoculated with an infectious agent. These variants appeared to be species-specific in that sequences isolated within a species were virtually identical, though sequences were strikingly different when compared between each species. In the present study, the nucleotide sequence of one of these variants, GBV-Alab, was extended to near-genome length. Similar to the other GB viruses, GBV-Alab appears to encode a single large polyprotein of 2967 amino acids that is post-translationally cleaved by cellular and viral proteases into the individual viral proteins. The structural proteins are found at the N-terminal end of the polyprotein, while the nonstructural proteins are found at the C teminus. Amino acid sequence comparisons of the large polyprotein demonstrate that GBV-Alab is 74% identical to GBV-A and 48% identical to GBV-C, sharing only marginal identity with GBV-B and HCV-1 at 27%. Examination of the GBV-Alab polyprotein reveals that structural motifs are conserved for a protease, a helicase and a replicase. Phylogenetic analysis of the polyprotein confirms previous results that GBV-Alab is a member of the Flaviviridae, distinct from GBV-B and HCV, though more closely related to GBV-A and GBV-C.
最近，从未经传染性病原体实验接种的不同猴种血清中分离出了几种GB病毒A新变种的基因片段。这些变种似乎具有物种特异性，即同一物种内分离出的序列几乎相同，不过不同物种间的序列差异显著。在本研究中，其中一个变种GBV-Alab的核苷酸序列被延伸至接近基因组长度。与其他GB病毒相似，GBV-Alab似乎编码一种由2967个氨基酸组成的单一大型多聚蛋白，该多聚蛋白在翻译后被细胞和病毒蛋白酶切割成各个病毒蛋白。结构蛋白位于多聚蛋白的N末端，而非结构蛋白位于C末端。大型多聚蛋白的氨基酸序列比较表明，GBV-Alab与GBV-A的同源性为74%，与GBV-C的同源性为48%，与GBV-B和HCV-1的同源性仅为27%，只有少量相同之处。对GBV-Alab多聚蛋白的研究表明，蛋白酶、解旋酶和复制酶的结构基序是保守的。多聚蛋白的系统发育分析证实了先前的结果，即GBV-Alab是黄病毒科的成员，与GBV-B和HCV不同，但与GBV-A和GBV-C的关系更为密切。
