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

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