Primary structure of the cleavage site associated with trypsin enhancement of rotavirus SA11 infectivity

The primary structure of the trypsin cleavage site in the outer layer protein VP3 of rotavirus SAU was determined. This cleavage enhances the infectivity of rotavirus SAU. Both VP8, one of the polypeptides generated by the cleavage, and VP3 had their a-NH2 blocked. Only VP5, the other polypeptide produced by the cleavage, was susceptible to sequential Edman degradation, indicating that it contained the new α-NH2 terminus generated by trypsin hydrolysis. The results indicated that purified VP5 is composed of two polypeptides with the following amino acid sequence at their N terminus: (a) ??VYTRAQPNQDA VVSKTS ... ; (b) AQPNQDAVVSKTS .... Sequencing of the DNA complementary to ds RNA segment 4 revealed a nucleotide sequence encoding the amino acid sequences indicated above, with only one different amino acid. From these results, the amino acid sequence of the site cleaved by trypsin was extended to cover the C termini (present in VP8). The following sequence, which contains two sites (indicated with asterisks) and can be cleaved by trypsin was deduced: ...VPVSIVSR*NIVYTR*AQPNQDIVVSKTS...