title: Ligand-integrin alpha v beta 3 interaction determined by photoaffinity cross-linking: a challenge to the prevailing model.
abstract: Integrin alpha(V)beta(3) plays a crucial role in angiogenesis, apoptosis, and bone remodeling, mainly by interacting with matrix proteins through recognition of an Arg-Gly-Asp (RGD) motif. Recently, a small cyclic RGD-containing alpha(V)beta(3)-ligand possessing a C-terminal photoreactive group was photo-cross-linked within beta(3)[99-118], in the N-terminus of the beta(3) chain [Bitan G et al. (1999) Biochemistry 38, 3414-3420]. In this paper, a photoreactive group at the N-terminus of the RGD-ligand is shown to interact within beta(3)[167-171], approximately 60 residues C-terminal to the previously identified domain. On the basis of these findings, a model of the putative I-like domain of the beta(3) subunit, homologous to alpha(M)-, alpha(L)-, and alpha(2)-I-domains, reveals that the beta(3)[99-118] and beta(3)[167-171] contact sites are close to each other and are on the opposite side relative to the metal ion-dependent adhesion site (MIDAS) motif. These observations contradict the prevailing model that proposes proximity between metal- and RGD-binding sites on the I-like domain. Our data suggest that either the I-like domain structure predicted for beta(3) is incorrect, or there is no spatial proximity between the RGD-binding site and the MIDAS motif in the I-like domain. Our results indicate that the current models for ligand-receptor interaction should be revisited.
authors.affiliation: Division of Bone and Mineral Metabolism, Charles A. Dana and Thorndike Laboratories, Department of Medicine, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, Massachusetts 02215, USA.
authors.forename: G
authors.initials: G
authors.lastname: Bitan
authors.forename: L
authors.initials: L
authors.lastname: Scheibler
authors.forename: D F
authors.initials: DF
authors.lastname: Mierke
authors.forename: M
authors.initials: M
authors.lastname: Rosenblatt
authors.forename: M
authors.initials: M
authors.lastname: Chorev
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001577:Benzophenones / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002460:Cell Line; D003198:Computer Simulation; D003432:Cross-Linking Reagents / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism; D019920:Photoaffinity Labels / Q000737:chemistry / Q000378:metabolism*; D019030:Receptors, Vitronectin / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics
chemical_list: D001577:Benzophenones; D003432:Cross-Linking Reagents; D008024:Ligands; D009842:Oligopeptides; D019920:Photoaffinity Labels; D019030:Receptors, Vitronectin; D011994:Recombinant Proteins; C047723:benzophenone; C047981:arginyl-glycyl-aspartic acid