Synthesis and processing of the equine herpesvirus 1 glycoprotein M.
In a previous report, the function of the equine herpesvirus 1 (EHV-1) glycoprotein M (gM) homolog was investigated. It was shown that EHV-1 gM is involved in both virus entry and direct cell-to-cell spread of infection (N. Osterrieder et al., J. Virol. 70, 4110-4115, 1996). In this study, experiments were conducted to analyze the synthesis, posttranslational processing, and the putative ion channel function of EHV-1 gM. It was demonstrated that EHV-1 gM is synthesized as an Mr 44,000 polypeptide, which is cotranslationally N-glycosylated to an Mr 46,000-48,000 glycoprotein. The Mr 46,000-48,000 gM moiety is processed to an Mr 50,000-55,000 glycoprotein, which is resistant to treatment with endoglycosidase H, indicating that processing occurs in the Golgi network. EHV-1 gM forms a dimer in infected cells and the virion, as was demonstrated by the presence of an Mr 105,000-110,000 gM-containing band in electrophoretically separated lysates of infected cells and purified extracellular virions. The Mr 105,000-110,000 protein band containing gM was also observed in lysates of cells that had been transfected with EHV-1 gM DNA. The translation of EHV-1 gM is initiated at the first in-frame methionine of the gM open reading frame as shown by transient transfection experiments of full-length gM and a truncated gM lacking the aminoterminal 83 amino acids. Functional expression of EHV-1 gM in Xenopus laevis oocytes together with voltage-clamp analyses demonstrated that gM per se does not exhibit ion channel activity as had been speculated from the predicted structure of the polypeptide.
Osterrieder
N
N
Institute for Medical Microbiology, Infectious and Epidemic Diseases, Ludwig-Maximilians-University München, Munich, Germany. klaus.osterrieder@lrz.uni-muenchen.de
Neubauer
A
A
Fakler
B
B
Brandmüller
C
C
Seyboldt
C
C
Kaaden
O R
OR
Baines
J D
JD
D000818:Animals; D019556:COS Cells; D016521:Electrophoresis, Gel, Pulsed-Field; D006031:Glycosylation; D004861:Herpesvirus 1, Equid / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D014764:Viral Proteins / Q000096:biosynthesis / Q000378:metabolism*
D007473:Ion Channels; D014764:Viral Proteins; D008715:Methionine