UL20 protein interacts with gM in virus-infected cells. Vero cell monolayers were infected with HSV-1(F) or HSV-1(F)-YE102-VC1 (having UL20 protein tagged with the 3×FLAG epitope and gK tagged with the V5 epitope). Cellular extracts were prepared at 24 hpi, and the presence of gB, gM, or UL20 was detected using Western immunoblots after immunoprecipitation (IP) with designated antibodies. Lanes 1, 3, 5, and 7, antigen from HSV-1(F)-infected cells; lanes 2, 4, 6, and 8, antigen from HSV-1(F)-YE102-VC1-infected cells; lane M demarcates positions of molecular mass markers (10 to 250 kDa; Bio-Rad). Anti-gB (α-gB), anti-gM (α-gM), and anti-FLAG (α-UL20) denote probed antibodies, and gB-IP, gM-IP, and UL20-IP (FLAG-IP) represent antibodies used for immunoprecipitation. gB, H, L, gM, and UL20 denote gB, heavy chain, light chain, gM, and UL20 proteins, respectively.