Cloning and sequence analysis of murine cytomegalovirus protease and capsid assembly protein genes.

The murine cytomegalovirus UL80 open reading frame was cloned and the predicted amino acid sequence compared with those from other herpesviruses. The open reading frame encodes a fused protease-capsid assembly protein precursor and maintains conserved features including the active site serine, conserved regions CD1 through CD5, the release and maturation sites, and a potential internal cleavage site within the protease. However, the murine cytomegalovirus protease differs in comparison with the other proteases because it contains a unique 15-16 amino acid insertion between CD3 and CD1. The assembly protein sequences are relatively divergent, but they can be arranged into groups defined by herpesvirus subfamily, with each group possessing a conserved motif at its carboxyl terminus.