Characteristics of fibrinogen binding to the domain of CD11c, an alpha subunit of p150,95.
beta2 integrins on leukocytes play important roles on cell-cell or cell-matrix adhesion through their ability to bind multiple ligands. The alpha subunits of leukocyte CD11/CD18 integrins contain an approximately 200-amino-acid inserted domain (I-domain) which is implicated in ligand binding function. To understand the characteristics of ligand binding to the alpha subunit of beta2 integrin p150,95 (CD11c/CD18), a recombinant form of the I-domain of CD11c was generated and analyzed for the interaction with fibrinogen, one of the ligands of p150,95. It was found that the CD11c I-domain bound fibrinogen specifically. Fibrinogen binding to the CD11c I-domain was inhibited by a molar excess of fragment E, a central domain of fibrinogen, and not by that of fragment D, a distal domain of fibrinogen, suggesting that CD11c/CD18 recognizes a central domain of fibrinogen. Divalent cations such as Mg(2+) and Mn(2+) were required for fibrinogen binding to the CD11c I-domain. Also alanine substitutions on the putative metal binding sites of the CD11c I-domain such as Asp(242) and Tyr(209) reduced its ability to bind fibrinogen. These data reinforce the fact that the divalent cation is a prerequisite for ligand binding of the CD11c I-domain.
Nham
S U
SU
Biology Group, Division of Science Education, Kangwon National University, Choonchun, Kangwon, 200-701, Korea. sunham@cc.kangwon.ac.kr
D019943:Amino Acid Substitution; D001665:Binding Sites / Q000235:genetics; D005340:Fibrinogen / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D016167:Integrin alphaXbeta2 / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship
D016167:Integrin alphaXbeta2; D011993:Recombinant Fusion Proteins; D005340:Fibrinogen