SUMMARY:Nucleotide and deduced amino acid sequences of the outer capsid proteins VP4 and VP7 of a murine rotavirus strain (YR-1) isolated in Japan were determined.Comparisons of the VP7 amino acid sequence of YR-1 with other murine rotavirus strains (EB, EW, EC, EL and EHP) (1) showed that YR-1 was highly homologous to EB, EW, EC, EL and EHP. Moreover, YR-1 was more closely related to strains representing G3 than to any other G type. Analysis of the VP4 amino acid sequence revealed that YR-1 was highly homologous to EB, EW, EC and EL [tentatively P17 (1)], and more closely related to EHP [tentatively P18 (1)] than to any other P type.Enzyme immunoassay with monoclonal antibodies against G types (KU-4 and BH49 for G1, S2-2G10 and BW36 for G2, YO-IE2 and BC5 for G3; and ST-2G7 and BE18 for G4) and against a P type (YO-1S3, KU-12H and YO-2C2 for P8) showed no reactivity.These results indicate that YR-1 is highly homologous to EB, EW, EC and EL.