Heparin-binding domain of bovid herpesvirus 1 glycoprotein gIII

Bovid herpesvirus 1 (BHV-1) glycoprotein gIII functions as a major virus attachment protein through binding to a heparin-like moiety on the host cells. To identify the functional domain, a panel of gIII deletion mutants was constructed, expressed in COS-7 cells, and examined for heparin-binding activity. Mutants with deletion of amino acid residues 103-173 and 324-443 bound to heparin as well as full-length gIII, whereas a mutant with residues 172-337 deleted showed no binding to heparin. In another mutant, with residues 172-211 deleted, the activity was reduced by one-third. These data suggest that the amino acid sequence between residues 172 and 323 contains the functional domain of BHV-1 gIII for heparin-binding and that especially the sequence between residues 212-323 includes a critical site for the activity.