Sequence alterations in temperature-sensitive M-protein mutants (complementation group III) of vesicular stomatitis virus.

Sequences were determined of the coding regions of the M-protein genes of the Glasgow and Orsay strains of vesicular stomatitis virus (Indiana serotype) and of two group III (M-protein) mutants derived from each wild type. Synthetic primers were annealed with viral genomic RNA and extended with reverse transcriptase. The resulting high-molecular-weight cDNA was sequenced directly. Both Glasgow and Orsay wild types differed in 13 bases from a clone of the San Juan strain sequenced by J. K. Rose and C. J. Gallione (J. Virol. 39:519-528, 1981). Six of these base changes caused amino acid changes in each wild type, whereas seven were degenerate. The Orsay and Glasgow sequences resembled each other more closely than either resembled that of Rose and Gallione, differing in eight nucleotides and four amino acids. Each of the four mutants, however, differed from its parent wild type in only one or two point mutations. Every mutation caused a change either from or to a charged amino acid; the change for tsG31 was Lys (position 215) to Glu, the change for tsO23 was Gly (position 21) to Glu, the change for tsO89 was Ala (position 133) to Asp, the changes for tsG33 were Lys (position 204) to Thr and Glu (position 214) to Lys. The charge differences predicted from these amino acid changes was confirmed by nonequilibrium pH gradient electrophoresis for tsG31, tsG33, tsO23, and the two wild types. These mutations affect residues spanning nearly 85% of the linear sequence, although the mutants possess nearly identical phenotypic properties.