2nwg
From Proteopedia
Structure of CXCL12:heparin disaccharide complex
Structural highlights
Function[SDF1_HUMAN] Chemoattractant active on T-lymphocytes, monocytes, but not neutrophils. Activates the C-X-C chemokine receptor CXCR4 to induce a rapid and transient rise in the level of intracellular calcium ions and chemotaxis. Also binds to another C-X-C chemokine receptor CXCR7, which activates the beta-arrestin pathway and acts as a scavenger receptor for SDF-1. SDF-1-beta(3-72) and SDF-1-alpha(3-67) show a reduced chemotactic activity. Binding to cell surface proteoglycans seems to inhibit formation of SDF-1-alpha(3-67) and thus to preserve activity on local sites. Acts as a positive regulator of monocyte migration and a negative regulator of monocyte adhesion via the LYN kinase. Stimulates migration of monocytes and T-lymphocytes through its receptors, CXCR4 and CXCR7, and decreases monocyte adherence to surfaces coated with ICAM-1, a ligand for beta-2 integrins. SDF1A/CXCR4 signaling axis inhibits beta-2 integrin LFA-1 mediated adhesion of monocytes to ICAM-1 through LYN kinase. Inhibits CXCR4-mediated infection by T-cell line-adapted HIV-1. Plays a protective role after myocardial infarction. Induces down-regulation and internalization of CXCR7 expressed in various cells. Has several critical functions during embryonic development; required for B-cell lymphopoiesis, myelopoiesis in bone marrow and heart ventricular septum formation.[1] [2] [3] [4] [5] [6] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedCXCL12 (SDF-1alpha) and CXCR4 are critical for embryonic development and cellular migration in adults. These proteins are involved in HIV-1 infection, cancer metastasis, and WHIM disease. Sequestration and presentation of CXCL12 to CXCR4 by glycosaminoglycans (GAGs) is proposed to be important for receptor activation. Mutagenesis has identified CXCL12 residues that bind to heparin. However, the molecular details of this interaction have not yet been determined. Here we demonstrate that soluble heparin and heparan sulfate negatively affect CXCL12-mediated in vitro chemotaxis. We also show that a cluster of basic residues in the dimer interface is required for chemotaxis and is a target for inhibition by heparin. We present structural evidence for binding of an unsaturated heparin disaccharide to CXCL12 attained through solution NMR spectroscopy and x-ray crystallography. Increasing concentrations of the disaccharide altered the two-dimensional (1)H-(15)N-HSQC spectra of CXCL12, which identified two clusters of residues. One cluster corresponds to beta-strands in the dimer interface. The second includes the amino-terminal loop and the alpha-helix. In the x-ray structure two unsaturated disaccharides are present. One is in the dimer interface with direct contacts between residues His(25), Lys(27), and Arg(41) of CXCL12 and the heparin disaccharide. The second disaccharide contacts Ala(20), Arg(21), Asn(30), and Lys(64). This is the first x-ray structure of a CXC class chemokine in complex with glycosaminoglycans. Based on the observation of two heparin binding sites, we propose a mechanism in which GAGs bind around CXCL12 dimers as they sequester and present CXCL12 to CXCR4. Structural and functional basis of CXCL12 (stromal cell-derived factor-1 alpha) binding to heparin.,Murphy JW, Cho Y, Sachpatzidis A, Fan C, Hodsdon ME, Lolis E J Biol Chem. 2007 Mar 30;282(13):10018-27. Epub 2007 Jan 29. PMID:17264079[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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