Role of HSV-1 UL45 protein in the pH-triggered gB conformation change. (A) UL45 protein content of HSV-1 ANG path virions. Two-fold dilutions of HSV-1 KOS or ANG path were blotted to nitrocellulose membrane. Blots were probed with polyclonal antibody specific for gB or UL45. (B) Reversible, pH-dependent conformational change in gB from virions lacking the UL45 protein. HSV-1 KOS UL45 D or KOS wild type virions were treated with pH as indicated in the legend to Figure 3A. Conformational change in gB was probed with the indicated antibodies.