COMPARATIVE SEQUENCE-ANALYSIS OF THE REOVIRUS-S4 GENES FROM 13 SEROTYPE-1 AND SEROTYPE-3 FIELD ISOLATES

The reovirus sigma 3 protein is a major outer capsid protein that may function to regulate translation within infected cells. To facilitate the understanding of sigma 3 structure and functions and the evolution of mammalian reoviruses, we sequenced cDNA copies of the S4 genes fro m 10 serotype 3 and 3 serotype 1 reovirus field isolates and compared these sequences with sequences of prototypic strains of the three reov irus serotypes. We found that the sigma 3 proteins are highly conserve d: the two longest conserved regions contain motifs proposed to functi on in binding zinc and double-stranded RNA. We used the 16 viral isola tes to investigate the hypothesis that structural interactions between sigma 3 and the cell attachment protein, sigma 1, constrain their evo lution and to identify a determinant within sigma 3 that is in close p roximity to the sigma 1 hemagglutination site.