Characterization of the protein encoded by gene UL49A of herpes simplex virus type 1.

Herpes simplex virus type 1 (HSV-1) gene UL49A potentially encodes a primary translation product of 91 residues with a signal sequence at the N terminus and a membrane anchor domain near the C terminus. Mutants were generated in this gene and utilized to characterize the encoded protein on SDS-PAGE as a 6.7 kDa species which fractionated with infected cell membranes, was a relatively abundant virion component, and was not detectably O-glycosylated. The protein was identified by microsequencing as a 68 residue polypeptide formed by removal of 23 residues from the N terminus of the primary translation product. Cleavage of the signal sequence was also demonstrated by in vitro transcription and translation in the presence of microsomal membranes. The UL49A protein was efficiently solubilized along with envelope proteins by treatment of virions with a non-ionic detergent but only in the presence of a reducing agent, suggesting that it may be an envelope protein that is disulphide-linked to the tegument. It is apparent from mutational analysis that the 10 amino acid residues at the C terminus are not essential for synthesis of the protein, signal sequence cleavage, targeting to membranes and virions, linkage to the tegument and growth of virus in cell culture.