Sequences of the four larger proteins of a porcine group C rotavirus and comparison with the equivalent group A rotavirus proteins.

The sequences of the four larger proteins of rotavirus group C (Cowden strain) are presented and compared with the sequences of the corresponding group A proteins. They exhibit a significant level of homology, allowing gene coding assignment for the group C rotavirus. The coding strategy of the group C virus RNA segment is the same as that for the group A large segments as one long open reading frame is present in each segment. The genome segment 1 encodes the structural protein VP1 which presents the RNA-dependent RNA polymerase consensus motifs. The VP1 protein is the most highly conserved between the rotaviruses of groups A and C. The genome segment 2 encodes the VP2 protein. The deduced protein sequence does not present the putative leucine zippers identified in the group A protein but its amino terminal is hydrophilic and highly charged as previously noted for the group A protein. The genome segment 3 encodes for a protein homologous to the group A outer capsid protein VP4. As observed among the various group A sequences, the amino terminal is the region presenting the fewest similarities. A cleavage region and a putative fusion motif similar to those present in the group A viruses have been identified. For this protein the comparison has been extended to the IDIRV [corrected] VP3 previously sequenced and indicates that groups A and C VP4 proteins are much more related to each other than to the group B equivalent. The genome segment 4 encodes for a protein showing an approximate 40% sequence identity to the minor core protein, VP3, of the group A rotavirus. This remarkable conservation of primary structures argues for severe functional constraint on the evolution of these proteins.