A lipid modified ubiquitin is packaged into particles of several enveloped viruses

An anti-ubiquitin cross-reactive protein which migrates more slowly (6.5 kDa) by SDS-PAGE than ubiquitin was identified in African swine fever virus particles. This protein was extracted into the detergent phase in Triton X-114 phase separations, showing that it is hydrophobic, and was radiolabelled with both [3H]palmitic acid and [32P]orthophosphate. This indicates that the protein has a similar structure to the membrane associated phosphatidyl ubiquitin described in baculovirus particles. A similar molecule was found in vaccinia virus and herpes simplex virus particles, suggesting that it may be a component of uninfected cell membranes, which is incorporated into membrane layers in virions during morphogenesis.