The authentic sequence of rotavirus SA11 nonstructural protein NSP4

Recent studies demonstrate that the rotavirus nonstructural protein NSP4 functions as an enterotoxin and plays an important role in viral pathogenesis. Previous in vitro studies of NSP4 have used a cDNA clone of gene 10 derived from the prototypic rotavirus strain, SA11. We recently compared the sequence of the commonly used NSP4 cDNA with the sequence obtained from several SA11 isolates by direct sequencing of reverse transcription polymerase chain reaction products. One codon difference was identified between the cDNA clone and the SA11 virus isolates, and this resulted in a predicted amino acid substitution at position 47. The cDNA sequence specifies an asparagine at position 47, and the SA11 virus gene 10 encodes a hisitidine. To determine if this amino acid substitution altered the function of NSP4, we analyzed the ability of both NSP4-Asn47 and NSP4-His47 to regulate intracellular calcium levels and exhibit cell cytotoxicity. Our results indicate that the expression of NSP4-His47 from a recombinant baculovirus displays enhanced cytotoxicity and calcium flux.