The nucleotide sequence of the U(L)10 (glycoprotein M) and the U(L)11 homologs of Marek's Disease Virus 1 strain GA was determined. The U(L)10 open reading frame encodes a type III membrane protein of 424 amino acids that contains eight hydrophobic domains and two consensus N-linked glycosylation sites. The U(L)11 homologous gene encodes an 84 amino acid polypeptide, and contains a highly conserved myristylation site at its aminoterminus. By analysis of infected-cell RNA with strand-specific RNA probes, transcription of both U(L)10 and U(L)11 in infected cells was demonstrated. Coupled in vitro transcription-translation confirmed that the U(L)10 product is a 47 kD N-glycosylated viral protein that aggregated upon boiling, whereas the U(L)11 protein exhibited a size of 12 kD after in vitro translation.