Equine cytomegalovirus: structural proteins of virions and nucleocapsids

Enveloped virions and nucleocapsids of equine cytomegalovirus (ECMV; equine herpesvirus type 2) have been purified from the supernatants and the nuclear extracts of infected rabbit kidney (RK) cells, respectively, and their structural protein compositions have been analyzed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that ECMV nucleocapsids were composed of nine proteins (average molecular weights = 148K, 52K, 49.5K, 46K, 43.5K, 38.5K, 27K, 20K, and 18K), which together constituted 89% of the total nucleocapsid protein on the basis of incorporated 3H-labeled amino acids. The 148K protein comprised 47.3% of the total protein and thus appeared to be similar in molecular weight and proportional composition to the major capsid proteins of other herpesviruses. Purified virions were composed of 37 proteins whose average molecular weights ranged from 14K to greater than 200K. Three intense glycoprotein bands (83K, 78K, and 73.5K) as well as four less intensely labeled glycoproteins were detected in [3H]glucosamine-labeled virion preparations. At least 14 structural proteins were readily detected in extracts of infected cells which had been [35S]methionine labeled late in infection, and 11 of these were immunoprecipitated by rabbit antiserum against purified virions. The protein composition of ECMV differs substantially from those of equine herpesvirus type 1 and type 3 as well as from those of other herpesviruses.