HSV gK and UL20p interact in infected cells. Vero cells were infected with gKD3prtC/UL20FLAG virus, which specifies the differentially epitope-tagged gK (prtC) and UL20p (FLAG) proteins. Infected cell lysates were either directly loaded (no precipitation) or immunoprecipitated with antibodies to gK (αprtC), UL20p (αFLAG), or gD (αgD). Blots of SDS-PAGE-separated immunoprecipitates were probed with anti-prtC (αgK), anti-FLAG (αUL20), or αgB and αgD in combination in order to detect coimmunoprecipitated proteins. For control purposes, blots of SDS-PAGE-separated cellular extracts were probed for the presence of gK, UL20p, gD, and gB (no precipitation).