BOVINE HERPESVIRUS-1 GLYCOPROTEIN-M FORMS A DISULFIDE-LINKED HETERODIMER WITH THE U(L)49.5 PROTEIN

Nine glycoproteins (gB, gC, gD, gE, gG, gH, gI, gK, and gL) have been identified in bovine herpesvirus 1 (BHV-1). gM has been identified in many other alpha-, beta-, and gammaherpesviruses, in which it appears to play a role in membrane penetration and cell-to-cell fusion. We sou ght to express BHV-1 open reading frame U(L)10, which encodes gM, and specifically identify the glycoprotein. We corrected a frameshift erro r in the published sequence and used the corrected sequence to design coterminal peptides from the C terminus. These were expressed as gluta thione S-transferase fusion proteins in Escherichia call. The fusion p rotein containing the 63 C-terminal amino acids from the corrected gM sequence engendered antibodies that immunoprecipitated a 30-kDa protei n from in vitro translation reactions programmed with the U(L)10 gene. Proteins immunoprecipitated by this antibody from virus-infected cell s ran at 36 and 43 kDa in reducing sodium dodecyl sulfate-polyacrylami de gel electrophoresis (SDS-PAGE) and 43 and 48 kDa in nonreducing SDS -PAGE. Only the larger of the pair was present in virions. A 7-kDa pro tein was released from gM by reducing agents. The 7-kDa protein was no t recognized in Western blots probed with the anti-gM antibody but rea cted specifically with antibodies prepared against BHV-1 U(L)49.5, pre viously reported to be a 9-kDa protein associated with an unidentified 39-kDa protein (X. Liang, B. Chow, C. Raggo, and L. A. Babiuk, J. Vir ol. 70:1448-1454, 1996). This is the first report of a small protein c ovalently bound to any herpesvirus gM. Similar patterns of hydrophobic domains and cysteines in all known gM and U(L)49.5 homologs suggest t hat these two proteins may be linked by disulfide bonds in all herpesv iruses.