Molecular characterization of the guinea-pig cytomegalovirus glycoprotein L gene

Although the guinea pig cytomegalovirus (GPCMV) model is well suited to the study of vaccines for prevention of congenital CMV infection, there has be en limited molecular characterization of GPCMV glycoproteins. Since the in vivo co-expression of the human cytomegalovirus (HCMV) glycoprotein H (gH, gpUL75) with glycoprotein L (gL, gpUL115) may have relevance to CMV vaccine studies, these experiments were undertaken to test whether the GPCMV encod es a gL homolog. Sequencing of the EcoR I "G" fragment of the GPCMV genome identified an open reading frame (ORF) of 774 nucleotides capable of encodi ng a protein of 258 amino acids. Computer matrix analyses demonstrated iden tity between this ORF and the gL coding sequences of other betaherpesviruse s. Sequence analysis also identified an ORF with identity to the HCMV uraci l DNA glycosylase (UDG, UL114 gene). The GPCMV gL ORF encodes 6 cysteine re sidues, contains 3 potential N-linked glycosylation sites, and has a predic ted M-r of 29.7 kDa. Northern blot studies identified an abundant 2.7 kb "e arly" transcript from infected cells, the putative gL message. In vitro tra nslation of gL mRNA in reticulocyte lysate resulted in synthesis of 30 kDa polypeptide. A polyclonal antiserum was raised against a gL/glutathione-S-t ransferase fusion protein generated in E. coli using the pGEX expression sy stem. This antibody identified a 40-kDa virion-associated protein, the puta tive GPCMV gL, in immunoblot assays.