title: The requirement of the glutamic acid residue at the third position from the carboxyl termini of the laminin gamma chains in integrin binding by laminins.
abstract: Laminins are the major cell-adhesive proteins in the basement membrane, consisting of three subunits termed alpha, beta, and gamma. The putative binding site for integrins has been mapped to the G domain of the alpha chain, although trimerization with beta and gamma chains is necessary for the G domain to exert its integrin binding activity. The mechanism underlying the requirement of beta and gamma chains in integrin binding by laminins remains poorly understood. Here, we show that the C-terminal region of the gamma chain is involved in modulation of the integrin binding activity of laminins. We found that deletion of the C-terminal three but not two amino acids within the gamma1 chain completely abrogated the integrin binding activity of laminin-511. Furthermore, substitution of Gln for Glu-1607, the amino acid residue at the third position from the C terminus of the gamma1 chain, also abolished the integrin binding activity, underscoring the role of Glu-1607 in integrin binding by the laminin. We also found that the conserved Glu residue of the gamma2 chain is necessary for integrin binding by laminin-332, suggesting that the same mechanism operates in the modulation of the integrin binding activity of laminins containing either gamma1 or gamma2 chains. However, the peptide segment modeled after the C-terminal region of gamma1 chain was incapable of either binding to integrin or inhibiting integrin binding by laminin-511, making it unlikely that the Glu residue is directly recognized by integrin. These results, together, indicate a novel mechanism operating in ligand recognition by laminin binding integrins.
authors.affiliation: Laboratory of Extracellular Matrix Biochemistry, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ido
authors.forename: Aya
authors.initials: A
authors.lastname: Nakamura
authors.forename: Reiko
authors.initials: R
authors.lastname: Kobayashi
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Ito
authors.forename: Shaoliang
authors.initials: S
authors.lastname: Li
authors.forename: Sugiko
authors.initials: S
authors.lastname: Futaki
authors.forename: Kiyotoshi
authors.initials: K
authors.lastname: Sekiguchi
mesh_terms: D000595:Amino Acid Sequence; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D017353:Gene Deletion; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D007797:Laminin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D016023:Integrins; D007797:Laminin; D011994:Recombinant Proteins; D018698:Glutamic Acid