Analysis of the biochemical properties of, and complex formation between, glycoproteins H and L of the gamma2 herpesvirus bovine herpesvirus-4.

Genes encoding glycoprotein gH and gL homo- logues were localized in the genome of the gamma- herpesvirus bovine herpesvirus-4 (BHV-4). Both genes were sequenced and glutathione S-trans- ferase fusion proteins were produced and used to immunize rabbits against the translation products of the two genes. The anti-gH serum recognized a protein with an apparent molecular mass (MM) of 110 kDa both in infected cells and in virions. This protein was sensitive to endo- β- N-acetylglucos- aminase-H (endoH) and endoglycosidase F-N-gly- cosidase F (endoF-PNGaseF) digestion. A protein with the same relative mobility was immunopre- cipitated from infected cells radiolabelled with [3H]glucosamine which confirmed that this product (gp110), now designated BHV-4 gH, was glycosylated. Western blotting with the anti-gL serum detected in infected cells a product with an apparent MM ranging from 31–35 kDa and diffusely migrating proteinspeciesrangingfrom45–65 kDa.Tunica- mycin, monensin, endoH or endoF-PNGaseF treatments showed that both the 31–35 kDa and the 45–65 kDa proteins were glycosylated, gp31–35 being a precursor of the 45–65 kDa glycoprotein species. In radioimmunoprecipitation assays, the anti-gL serum immunoprecipitated from infected cells two glycosylated proteins with apparent MMs of 31–35 kDa (gp31–35) and 45–55 kDa (gp45–55). However a third glycoprotein, gp110, was also immunoprecipitated together with gp31–35 and gp45–55. gp110 and gp45–55 were subsequently confirmed to be virion glycoproteins corresponding to mature forms of BHV-4 gH and gL respectively. In addition, the present study clearly demonstrated complex formation between BHV-4 gH and gL both in virions and in infected cells.