title: Examination of Glycosaminoglycan Binding Sites on the XCL1 Dimer.
abstract: Known for its distinct metamorphic behavior, XCL1 interconverts between a canonical chemokine folded monomer (XCL1mon) that interacts with the receptor, XCR1, and a unique dimer (XCL1dim) that interacts with glycosaminoglycans and inhibits HIV-1 activity. This study presents the first detailed analysis of the GAG binding properties of XCL1dim. Basic residues within a conformationally selective dimeric variant of XCL1 (W55D) were mutated and analyzed for their effects on heparin binding. Mutation of Arg23 and Arg43 greatly diminished the level of heparin binding in both heparin Sepharose chromatography and surface plasmon resonance assays. To assess the contributions of different GAG structures to XCL1 binding, we developed a solution fluorescence polarization assay and correlated affinity with the length and level of sulfation of heparan sulfate oligosaccharides. It was recently demonstrated that the XCL1 GAG binding form, XCL1dim, is responsible for preventing HIV-1 infection through interactions with gp120. This study defines a GAG binding surface on XCL1dim that includes residues that are important for HIV-1 inhibition.
authors.affiliation: Department of Biochemistry, Medical College of Wisconsin , Milwaukee, Wisconsin 53226, United States.
authors.forename: Jamie C
authors.initials: JC
authors.lastname: Fox
authors.affiliation: Department of Biochemistry, Medical College of Wisconsin , Milwaukee, Wisconsin 53226, United States.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Tyler
authors.affiliation: Department of Biochemistry, Medical College of Wisconsin , Milwaukee, Wisconsin 53226, United States.
authors.forename: Francis C
authors.initials: FC
authors.lastname: Peterson
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, Department of Pharmacology, University of California at San Diego , La Jolla, California 92093, United States.
authors.forename: Douglas P
authors.initials: DP
authors.lastname: Dyer
authors.affiliation: Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: Fuming
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Linhardt
authors.affiliation: Skaggs School of Pharmacy and Pharmaceutical Sciences, Department of Pharmacology, University of California at San Diego , La Jolla, California 92093, United States.
authors.forename: Tracy M
authors.initials: TM
authors.lastname: Handel
authors.affiliation: Department of Biochemistry, Medical College of Wisconsin , Milwaukee, Wisconsin 53226, United States.
authors.forename: Brian F
authors.initials: BF
authors.lastname: Volkman
mesh_terms: D001665:Binding Sites; D019744:Chemokines, C / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000737:chemistry / Q000378:metabolism*; D015658:HIV Infections / Q000235:genetics / Q000378:metabolism; D015497:HIV-1 / Q000378:metabolism; D006493:Heparin / Q000737:chemistry / Q000378:metabolism; D006497:Heparan Sulfate / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D017354:Point Mutation; D011485:Protein Binding; D017510:Protein Folding; D055503:Protein Multimerization
chemical_list: D019744:Chemokines, C; D006025:Glycosaminoglycans; D006493:Heparin; D006497:Heparan Sulfate; C092390:XCL1 protein, human
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