Classical swine fever virus (CSFV) envelope glycoprotein Erns 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 Erns gene was codon optimized for expression in the yeast Pichia pastoris. A C-terminally truncated Erns recombinant protein lacking the previously identified heparin-binding domain (HBD) bound to heparin column, suggesting the presence of another HBD in CSFV Erns. Sequence analyses of the CSFV Erns 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 Erns has been detected, and the two basic amino acids K303 and K306 are crucial for binding activity to heparin matrix and cell-surface GAGs.,Copyright ? 2019 Elsevier B.V. All rights reserved.