title: Integrin alpha 2 I-domain is a binding site for collagens.
abstract: Integrins alpha 1 beta 1 and alpha 2 beta 1 are major cellular receptors for collagens. The alpha 1 and alpha 2 subunits contain a approximately 200 amino acid inserted domain (I-domain) in their N-terminal region and, because of the homology between the I-domains and the collagen-binding A-domains of von Willebrand factor, it has been suggested that the I-domains might mediate the collagen-binding functions of alpha 1 beta 1 and alpha 2 beta 1. In order to fully investigate this hypothesis, we have generated recombinant human alpha 2 I-domain (r alpha 2I) by reverse transcriptase-polymerase chain reaction/bacterial expression and tested its ability to mediate the collagen-binding functions of alpha 2 beta 1. R alpha 2 I binds specifically to type I collagen in a concentration-dependent manner: binding is cation dependent and, like the complete receptor, is supported by magnesium and manganese ions but not by calcium ions. R alpha 2I is recognised by anti-functional anti-alpha 2 monoclonal antibodies 6F1, 5E8 and P1E6 in capture ELISAs, and anti-functional antibodies inhibited r alpha 2I-collagen binding. In addition, r alpha 2I inhibits cell spreading on collagen. R alpha 2I is therefore a collagen-binding domain and can account for many of the collagen-binding functions of integrin alpha 2 beta 1. We have also determined the collagen specificity of r alpha 2I and found that it binds types I, II and XI collagen.
authors.affiliation: School of Biological Sciences, University of Manchester, UK.
authors.forename: D
authors.initials: D
authors.lastname: Tuckwell
authors.forename: D A
authors.initials: DA
authors.lastname: Calderwood
authors.forename: L J
authors.initials: LJ
authors.lastname: Green
authors.forename: M J
authors.initials: MJ
authors.lastname: Humphries
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D001483:Base Sequence; D002413:Cations, Divalent / Q000494:pharmacology; D003001:Cloning, Molecular; D003094:Collagen / Q000302:isolation & purification / Q000378:metabolism*; D017931:DNA Primers; D004926:Escherichia coli; D005260:Female; D006801:Humans; D039222:Integrin alpha1beta1; D039421:Integrin alpha2; D016023:Integrins / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D010920:Placenta / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D051381:Rats; D038981:Receptors, Collagen; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D002413:Cations, Divalent; D017931:DNA Primers; D039222:Integrin alpha1beta1; D039421:Integrin alpha2; D016023:Integrins; D038981:Receptors, Collagen; D011994:Recombinant Proteins; D003094:Collagen