A comparison of the nucleotide sequences of cognate NS2 genes of three different orbiviruses

The genes encoding nonstructural protein NS2 of African horsesickness virus (AHSV) and epizootic hemorrhagic disease virus (EHDV) were cloned, sequenced, and compared to the NS2 gene of bluetongue virus (BTV). Nucleotide similarity ranged from 53 to 60%. The length of the proteins varied from 376 amino acids (EHDV) to 365 amino acids (AHSV). The N-terminal half of NS2 is more conserved (+/- 58% similarity) among the three orbiviruses, while the C-terminal half contains a 120 amino acid region of low similarity (18%). The variable region has a high content of alpha-helix conformation and a hydrophilic character. A short region of 9 amino acids contains 5 amino acids that are either similar or identical in single-stranded RNA binding proteins of BTV, EHDV, AHSV, reovirus and rotavirus.