Mutational analysis of the major heparan sulfate-binding domain of herpes simplex virus type 1 glycoprotein C

Heparan sulfate (HS) has been identified as a receptor molecule for numerou s microbial pathogens, including herpes simplex virus type 1 (HSV-1). To fu rther define the major MS-binding domain of the HSV-1 attachment protein, i .e. glycoprotein C (gC), virus mutants carrying alterations of either two n eighbouring basic amino acid residues or a single hydrophobic amino acid re sidue within the N-terminal domain of the protein (residues 26-227) were co nstructed. In addition, a mutant lacking the Asn148 glycosylation site was included in the study. Binding of purified mutated gC proteins to isolated HS chains showed that viruses with mutations at residues Arg(129,130), Ile1 42, Arg(143,145), Arg(145,147), Arg(151,155) and Arg(155,160) had significa ntly impaired MS binding, in contrast to the other mutations, including Asn 148, Impairment of the MS-binding activity of gC by these mutations had pr ofound consequences for virus attachment and infection of cells in which am ounts of HS exposed on the cell surface had been reduced. It is suggested t hat basic and hydrophobic residues localized at the Cys127-Cys144 loop of H SV-1 gC constitute a major MS-binding domain, with the most active amino ac ids situated near the C-terminal region of the two cysteines.