Abstract
The hemagglutinin-neuraminidase (HN) glycoprotein is utilized by human parainfluenza viruses for binding to the host cell. By the use of glycan array assays, we demonstrate that, in addition to the first catalytic-binding site, the HN of human parainfluenza virus type 1 has a second site for binding covered by N-linked glycan. Our data suggest that attachment of the first site to sialic acid (SA)-linked receptors triggers exposure of the second site. We found that both sites bind to α2-3-linked SAs with a preference for a sialyl-Lewis(x) motif. Binding to α2-3-linked SAs with a sulfated sialyl-Lewis motif as well as to α2-8-linked SAs was unique for the second binding site. Neither site recognizes α2-6-linked oligosaccharides.