Characterization of the Role of the N-Loop of MIP-1 in CCR5 Binding

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• 作者：Antoine Bondue ; Shu-chuan Jao ; Cé ; dric Blanpain ; Marc Parmentier ; and Patricia J. LiWang
• 刊名：Biochemistry
• 出版年：2002
• 出版时间：November 19, 2002
• 年：2002
• 卷：41
• 期：46
• 页码：13548 - 13555
• 全文大小：207K
• 年卷期：v.41,no.46(November 19, 2002)
• ISSN：1520-4995

文摘

MIP-1mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> is a CC-chemokine that plays a role in inflammation and host defense mechanismsby interacting with its specific receptor CCR5. CCR5 is a major coreceptor for macrophage-tropic humanimmunodeficiency virus (HIV), and as a consequence, MIP-1mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> can inhibit HIV entry. It is therefore ofinterest to understand how MIP-1mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> and other CCR5 ligands bind to their receptor, as such understandingcould lead to the rational design of more efficient HIV entry blockers. We have previously demonstratedthe importance of Phe13, and of basic residues of the 40's loop, in mediating high-affinity binding ofMIP-1mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> to CCR5. We have now investigated further the relative contribution of other MIP-1mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> residuesin the interaction of the chemokine with CCR5, by studying the functional consequences of point mutationswithin the N-loop and the 3₁₀ turn of MIP-1mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle">, affecting the charge, size, and H-bonding properties of theside chains. Our data suggest that, in addition to Phe13, three amino acids of the N-loop and 3₁₀ turn(Arg18, Lys19, and Arg22) interact with CCR5 through their positive charge. We also found that Pro21contributes to the CCR5 binding properties of MIP-1mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle">. Moreover, NMR spectroscopy has revealed thatthe presence of Tyr at position 15 is necessary for the proper folding of the chemokine. Our resultstherefore demonstrate that the binding determinants of MIP-1mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> consist of residues arranged on one surfaceof the protein, including most of the basic residues in MIP-1mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle">, as well as two key hydrophobic groups.The good correlation observed between the potency of the mutants in a functional assay and their bindingaffinity strongly argues that basic residues Arg18, Lys19, and Arg22 of MIP-1mages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> are essential for its CCR5binding properties, without a primary effect on CCR5 activation.