Sequence analysis and in vitro expression of genes 6 and 11 of an ovine group B rotavirus isolate, KB63: evidence for a non-defective, C-terminally truncated NSP1 and a phosphorylated NSP5

An ovine group B rotavirus (GBR) isolate, KB63, was isolated from faeces of a young goat with diarrhoea in Xinjiang, People's Republic of China. Seque nce determination and comparison of genes 6 and 11 with the corresponding s equences of GBR strains ADRV and IDIR showed that they were the cognate gen es encoding NSP1 and NSP5, respectively. While the overall identities of nu cleotide sequences between these two genes and the corresponding genes of s trains ADRV and IDIR were in the range 52.6-57.2%, the identities of deduce d amino acid sequences were only 34.9-46.3%. These results demonstrate that the substantial diversity of NSP1 observed among group A rotaviruses (GAR) also exists within GBRs and that a high degree of diversity also exists am ong NSP5 of GBRs, in contrast to GAR NSP5. The NSP1 gene of KB63 contains t hree ORFs, whereas the NSP1 genes of other GBR strains contain only two. OR Fs 2 and 3 of the KB63 gene may be derived from a single ORF corresponding to ORF2 of other GBR strains by the usage of a stop codon created by an ups tream single base deletion and single point mutations. In vitro expression studies showed that ORFs 1 and 2, but not 3, of gene 6 can be translated, s uggesting that ORF2 may encode a C-terminally truncated, potentially functi onal product. It may play a role, together with the product of ORF1, in vir us replication, as the virus can be passaged further in kids. Similarly, ge ne 1 1 can be translated in vitro. Like its counterpart in GARs, the protei n encoded by gene 11 was shown to be phosphorylated in vitro.