A Turn-like Structure “KKPE” Segment Mediates the Specific Binding of Viral Protein A27 to Heparin and Heparan Sulfate on Cell Surfaces

Abstract

). Importantly, T22K/A25K retained the binding specificity for HP and HS but not chondroitin sulfate, as shown by in vitro SPR and in vivo cell adhesion and competitive binding assays. Molecular modeling of the HBS was performed by dynamics simulations and provides an explanation of the specific binding mechanism in good agreement with the site-directed mutagenesis and SPR results. We conclude that a turn-like structure introduced by the KKPE segment in vaccinia viral envelope protein A27 is responsible for its specific binding to HP and to HS on cell surfaces.

Vaccinia Viral Protein A27 Is Anchored to the Viral Membrane via a Cooperative Interaction with Viral Membrane Protein A17

“…2A) shows only the signals originating from the flexible random coil (21-42 residues), whereas any remaining signals arising from the structured domains, such as CCD, DLD, and LZD (i.e. the A17 binding domain), were absent, consistent with the truncated A27 crystal structure (27) and previous reports (24,26,44). In contrast, as shown in Fig.…”

“…Previous studies have suggested that the N-and C-terminal domains are structurally distinct. For instance, the HBS is a flexible random coil, whereas the CCD, DLD, and LZD form rigid consecutive heptad repeated coiled coils (25,26). Despite their structural differences, both the N-terminal HBS and the C-terminal coiled coils cooperatively provide the specificity required for the interaction of the A27 protein with HS on the cell surface (26).…”

“…Despite their structural differences, both the N-terminal HBS and the C-terminal coiled coils cooperatively provide the specificity required for the interaction of the A27 protein with HS on the cell surface (26). Moreover, a penta-amino acid segment, KKPEA, in the flexible HBS forms a turn-like structure critical for heparin binding in vitro and HS binding on cells (26). Finally, the crystal structure of a truncated A27 protein (21-84 residues) was recently resolved and, consistent with previous results, revealed that the A27 protein assembles as a trimer containing two parallel ␣-helices and one antiparallel ␣-helix (27).…”

“…For instance, the HBS is a flexible random coil, whereas the CCD, DLD, and LZD form rigid consecutive heptad repeated coiled coils (25,26). Despite their structural differences, both the N-terminal HBS and the C-terminal coiled coils cooperatively provide the specificity required for the interaction of the A27 protein with HS on the cell surface (26). Moreover, a penta-amino acid segment, KKPEA, in the flexible HBS forms a turn-like structure critical for heparin binding in vitro and HS binding on cells (26).…”

Identification of Amino Acid Residues Important for Heparan Sulfate Proteoglycan Interaction within Variable Region 3 of the Feline Immunodeficiency Virus Surface Glycoprotein

“…Several methodologies have been used to study HSPG interactions, including mapping using synthetic peptides (21,34), site-directed mutagenesis (17,47,62), molecular modeling (2,4,30,47,51), high-resolution nuclear magnetic resonance (NMR) spectroscopy (2,25,47), X-ray crystallography (24,33,46), and hydrodynamic measurements (28). An early work based on heparin binding protein sequence comparisons in HIV-1 led to the proposition that two consensus heparin binding sequences, XBBXBX and XBBBXXBX motifs (where B stands for a basic and X for a neutral/hydrophobic amino acid), dictated such interactions (4).…”