Synthesis and processing of the envelope gp55-116 complex of human cytomegalovirus

The envelope of human cytomegalovirus has been reported to contain between three and eight glycoproteins. Major constituents of the envelope include two abundant glycoproteins with estimated molecular weights of 55,000 (gp55) and 116,000 (gp116). These two glycoproteins have been shown to exist as a disulfide-linked complex (gp55-116) within the envelope of mature virions. Utilizing a panel of monoclonal antibodies reactive with the gp55-116 complex, we characterized the synthesis and processing of these two virion proteins. Infected cells were shown to contain two glycosylated proteins of 160,000 and 150,000 daltons as well as the mature gp55 and gp116. Pulse-chase analysis indicated that gp150 was a precursor protein of gp160. The mature gp55 and gp116 were generated, in turn, by cleavage of gp160. Antigenic and structural analysis revealed that gp55 and gp116 shared little structural homology and no detectable antigenic cross-reactivity. The results of this study are discussed in relation to the synthesis of envelope proteins of other herpesviruses.