Protein structure of lymphocytic choriomeningitis virus: Identification of the virus structural and cell associated polypeptides

Abstract

Lymphocytic choriomeningitis virus (LCMV) has been found to contain 3 major structural polypeptides. The largest of these was shown to be a nonglycosylated nucleoprotein (NP) of approximately 63,000 daltons which was found internally in the virion and was associated with a dense ribonucleoprotein complex. Two glycopeptides, termed GP-1 and GP-2, of approximately 54,000 and 35,000 daltons, respectively, were shown to be localized on the virion surface by proteolytic digestion of intact virus. Peptide maps of GP-1 and GP-2 indicated that they were independent polypeptides and that GP-2 was not a cleavage product of GP-1. Furthermore, the tryptic peptide map of NP was distinct from the two glycopeptides. Pulse-labeling studies of the intracellular synthesis of LCMV specific polypeptides in infected BHK-21 cells demonstrated synthesis of the nucleoprotein by 6 hr after infection at a multiplicity of infection of 10, corresponding to the beginning of log phase of viral replication. In cytosol extracts of LCMV-infected cells enhanced by immune precipitation an additional apparently nonstructural glycopeptide with a molecular weight of 74–75,000 was observed. This cell associated glycopeptide, designated GP-C, was readily detectable after 24–48 hr of infection, and appeared to accumulate with increasing time of incubation. While the relationship of GP-C to the virion glycopeptides GP-1 and GP-2 has not been determined, immune precipitation studies have shown that GP-C does not share antigenic determinants with NP. The probable relationships between the polypeptides of lymphocytic choriomeningitis virus both to the pathogenesis of virus induced immune diseases and to the structure of other arenaviruses have been discussed.