Studies on the amino and carboxyl terminal amino acid sequences of reovirus capsid polypeptides.

Abstract

Abstract Techniques are described for isolating several reovirus capsid polypeptides in amounts sufficient for determination of amino and carboxyl terminal amino acid sequences and fingerprinting. Among them are chromatography on CM- and DEAE-Sephadex in the presence of urea, and gel filtration on agarose A-15 m in the presence of sodium dodecyl sulfate. Using a combination of these procedures, and starting with either virions or cores, polypeptides σ3, σ2, and μ2 have been obtained essentially pure. Polypeptides λ1 and λ2 have been obtained as a mixture which has so far not been resolved. All reovirus capsid polypeptides except μ2 possess blocked amino terminal amino acid residues. The amino terminal amino acid sequence of polypeptide μ2 is H2N-Pro-Gly-Gly-Val-Pro-. This suggests that polypeptide μ2 is derived from its precursor, polypeptide μ1, by cleavage of the amino terminal portion of the polypeptide chain. The carboxyl terminal regions of at least three of the five major reovirus capsid polypeptides are different. Polypeptide σ3 ends in -(val, val, leu)-COOH; polypeptide μ2 in -leu-(arg, tyr, tyr)-Arg-COOH; and either one or both of the two polypeptides λ1 and λ2 terminate(s) in -Arg-COOH, the adjacent amino acid sequence being different from that of μ2.