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

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 K³⁰³ and K³⁰⁶ significantly reduced the heparin-binding affinity of the protein. Further mutations of both T³¹⁰ and H³¹¹ 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 K³⁰³ and K³⁰⁶ are crucial for binding activity to heparin matrix and cell-surface GAGs.