Recognition of compartmentalized intracellular analogs of glycoprotein H of human cytomegalovirus.

Infected cell proteins immunoprecipitated from human cytomegalovirus (HCMV)-infected fibroblasts with glycoprotein H (gH)-specific conformation-dependent monoclonal antibody (mab 14-4 b) were found to consist of three components of 86 kDa, 89 kDa, and 125 kDa (gp 86, 89, and 125). Affinity purified antibodies from human convalescent serum reactive with an NH2-terminal epitope of gH recognized three polypeptides of comparable size in immunoblots, suggesting antigenic relatedness of these three components of the gH-complex. Using subcellular fractions for immunoblotting, gp 86 was identified as an endoglycosidase H (endo H)-sensitive gH-form present in the nuclear fraction whereas gp 89 and gp 125 were endo H-resistant and present in the membrane fraction or in virions. Incomplete endo H-digestion suggested that four of six predicted N-glycosylation sites of the gH molecule were occupied by carbohydrate side chains. Analysis under nonreducing conditions revealed that the compartmentalized as well as virion-associated gH analogs form high molecular weight complexes. The relation of the recognized gH analogs to the processing pathway of gH is discussed.