Comparison of the deduced matrix and fusion protein sequences of equine morbillivirus with cognate genes of the paramyxoviridae

The nucleotide sequence of the matrix protein of equine morbillivirus (EMV) was determined to be 1062 nucleotides and coded for a deduced protein of Mr 40148 having a net charge of +19 at neutral pH. The matrix protein gene was separated from the P and F genes by intercistronic regions of 546 and 469 nucleotides, respectively. The nucleotide sequence which coded for the F protein was 1641 nucleotides and coded for a deduced protein of 546 amino acids having an Mr of 60 447 and a charge +4 at neutral pH. Partial sequence information was also determined for the P/V proteins. M, P and F protein sequence comparisons revealed that a greater homology existed between EMV and known members of the morbillivirus genus than with other members of the paramyxoviridae and that this homology resided within the central half of the protein for the fusion protein, the C-terminal half of the matrix protein and at certain sites with the P protein. Far greater homology was seen between the morbilliviruses and EMV than for the other paramyxoviridae. It was inferred from phylogenetic analyses that EMV was a distantly related member of the morbillivirus genus. A conserved sequence of 18 nucleotides (assumed to be the transcriptional editing site) was present in the P gene of EMV. Insertion of a single nucleotide residue within this site generated the C-terminus of a V-like, cysteine rich protein. Likewise, a conserved ‘CTT’ intergenic region presumed to be the transcription termination and polyadenylation signal was present in EMV between the P-M-F genes. The close sequence homology of these sites with that of morbilliviruses also inferred that EMV was a member of the morbillivirus genus.