Characterization of the interactions of vMIP-II, and a dimeric variant of vMIP-II, with glycosaminoglycans.
Chemokines are important immune proteins, carrying out their function by binding to glycosaminoglycans (GAGs) on the endothelial surface and to cell surface chemokine receptors. A unique viral chemokine analogue, viral macrophage inflammatory protein-II (vMIP-II), encoded by human herpesvirus-8, has garnered interest because of its ability to bind to multiple chemokine receptors, including both HIV coreceptors. In addition, vMIP-II binds to cell surface GAGs much more tightly than most human chemokines, which may be the key to its anti-inflammatory function in vivo. The goal of this work was to determine the mechanism of binding of GAG by vMIP-II. The interaction of vMIP-II with a heparin-derived disaccharide was characterized using NMR. Important binding sites were further analyzed by mutagenesis studies, in which corresponding vMIP-II mutants were tested for GAG binding ability using heparin chromatography and NMR. We found that despite having many more basic residues than some chemokines, vMIP-II shares a characteristic binding site similar to that of its human analogues, utilizing basic residues R18, R46, and R48. Interestingly, a particular mutation (Leu13Phe) caused vMIP-II to form a pH-dependent CC chemokine-type dimer as determined by analytical ultracentrifugation and NMR. To the best of our knowledge, this is the first example of engineering a naturally predominantly monomeric chemokine into a dissociable dimer by a single mutation. This dimeric vMIP-II mutant binds to heparin much more tightly than wild-type vMIP-II and provides a new model for studying the relationship between chemokine quaternary structure and various aspects of function. Structural differences between monomeric and dimeric vMIP-II upon GAG binding were characterized by NMR and molecular docking.
Zhao
Bo
B
University of California, 5200 North Lake Road, Merced, California 95343, USA.
Liwang
Patricia J
PJ
D001665:Binding Sites; D018925:Chemokines / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D004187:Disaccharides / Q000378:metabolism; D006025:Glycosaminoglycans / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism; D019288:Herpesvirus 8, Human / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D055503:Protein Multimerization
D018925:Chemokines; D004187:Disaccharides; D006025:Glycosaminoglycans; D050505:Mutant Proteins; C108059:vMIP-II; D006493:Heparin