THE SEQUENCE AND GENOMIC ORGANIZATION OF A GB VIRUS-A VARIANT ISOLATED FROM CAPTIVE TAMARINS

Recently, gene fragments of several novel variants of GB virus A were isolated from the serum of distinct monkey species that had not been e xperimentally inoculated with an infectious agent, These variants appe ared to be species-specific in that sequences isolated within a specie s were virtually identical, though sequences were strikingly different when compared between each species. In the present study, the nucleot ide sequence of one of these variants, GBV-A(lab), was extended to nea r-genome length, Similar to the other GB viruses, GBV-A(lab) appears t o encode a single large polyprotein of 2967 amino acids that is post-t ranslationally cleaved by cellular and viral proteases into the indivi dual viral proteins, The structural proteins are found at the N-termin al end of the polyprotein, while the nonstructural proteins are found at the C teminus. Amino acid sequence comparisons of the large polypro tein demonstrate that GBV-A(lab) is 74% identical to GBV-A and 48% ide ntical to GBV-C, sharing only marginal identity with GBV-B and HCV-1 a t 27%. Examination of the GBV-A,,, polyprotein reveals that structural motifs are conserved for a protease, a helicase and a replicase, Phyl ogenetic analysis of the polyprotein confirms previous results that GB V-A(lab) is a member of the Flaviviridae, distinct from GBV-B and HCV, though more closely related to GBV-A and GBV-C.