N-terminus of Classical swine fever virus strain TD96 glycoprotein Erns contains a potential heparin-binding domain

Abstract Classical swine fever virus (CSFV) envelope glycoprotein E rns has been shown to bind to cell surface sulphated-heparin-like glycosaminoglycans (GAGs), which participate in cell attachment of the virus. In this study, the CSFV E rns gene was codon optimized for expression in the yeast Pichia pastoris . A C-terminally truncated E rns recombinant protein lacking the previously identified heparin-binding domain (HBD) bound to heparin column, suggesting the presence of another HBD in CSFV E rns . Sequence analyses of the CSFV E rns coding region revealed a common potential N-terminal HBD at residues 301－311. Site-directed mutagenesis of the basic amino acids at K 303 and K 306 significantly reduced the heparin-binding affinity of the protein. Further mutations of both T 310 and H 311 had little effect. Thus, a novel potential heparin-binding site near the N-terminus of CSFV strain TD96 E rns has been detected, and the two basic amino acids K 303 and K 306 are crucial for binding activity to heparin matrix and cell-surface GAGs.