Comparative sequence analysis of the reovirus S4 genes from 13 sero type 1 and serotype 3 field isolates

The reovirus σ3 protein is a major outer capsid protein that may function to regulate translation within infected cells. To facilitate the understanding of σ3 structure and functions and the evolution of mammalian reoviruses, we sequenced cDNA copies of the S4 genes from 10 serotype 3 and 3 serotype 1 reovirus field isolates and compared these sequences with sequences of prototypic strains of the three reovirus serotypes. We found that the σ3 proteins are highly conserved: the two longest conserved regions contain motifs proposed to function in binding zinc and double-stranded RNA. We used the 16 viral isolates to investigate the hypothesis that structural interactions between σ3 and the cell attachment protein, σ1, constrain their evolution and to identify a determinant within σ3 that is in close proximity to the σ1 hemagglutination site.