Expression of Reovirus Type 3 (Dearing) 1 and s Polypeptides in Escherichia coli

Abstract

Summary The revoirus S1 gene codes for two polypeptides: σ1 and σs. In order to characterize the structure and function of the σ1 polypeptide, we have expressed the σ1 protein in Escherichia coli. The S1 gene from mammalian reovirus type 3 (Dearing strain) and the variant K strain were subcloned into an expression vector containing the tac (trp-lac) promoter designed to express foreign gene products in E. coli efficiently. The hybrid plasmids, upon induction with isopropyl-β-d-thiogalactopyranoside, expressed two polypeptides that were detected by [35S]methionine labelling. One of the induced proteins had a relative molecular mass (M r) of approx. 46 000 and corresponded to σ1, as shown by immunoprecipitation with goat anti-reovirus antibody and a monoclonal antibody against σ1. The second induced protein had a M r of approx. 12 000 and was very similar to σs as judged by comparative tryptic peptide map analysis. Protein σ1 produced in E. coli was shown to be functional as judged from its ability to bind to mouse L fibroblasts.