Purification and characterization of integrin alpha 9 beta 1.
A new beta 1-containing integrin was isolated from rat liver by affinity chromatography on Sepharose conjugated with the peptide GRGDSPC. The interaction was weakened but not abolished when the arginine and/or aspartic acid in the peptide were replaced with lysine and glutamic acid, respectively. In contrast, the cysteine was necessary for binding of the integrin. The beta 1-associated protein, referred to as alpha 9, had an N-terminal amino acid sequence related to but distinct from previously described integrin alpha-subunits. In addition, an internal peptide sequence was obtained which confirmed that the protein is a new member of the family of integrin alpha-subunits. An antiserum raised against a synthetic peptide corresponding to amino acids 1-16 of alpha 9 reacted specifically with this protein and was used to identify alpha 9 in several tissues. The integrin alpha 9 beta 1 was not retained on Sepharose conjugated with Englebreth-Holm-Swarm tumor (EHS)-laminin, collagen type I, or a 105-kDa cell-binding fragment of fibronectin. However, it did bind specifically to EHS-laminin and collagen type I adsorbed to plastic microtiter wells. The sites of the interactions were localized to fragment E8 of EHS-laminin and to cyanogen bromide fragment 8 of collagen alpha 1(I) and were not inhibited by soluble RGD-containing peptides. The results indicate that alpha 9 beta 1 is a widely distributed laminin/collagen receptor which may have additional, yet unidentified ligands.
Department of Medical and Physiological Chemistry, University of Uppsala, Sweden.
E
E
Forsberg
B
B
Ek
A
A
Engström
S
S
Johansson
D000595:Amino Acid Sequence; D000818:Animals; D002846:Chromatography, Affinity; D003094:Collagen / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005353:Fibronectins / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D007797:Laminin / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009132:Muscles / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D009842:Oligopeptides; D009928:Organ Specificity; D011485:Protein Binding; D051381:Rats; D038981:Receptors, Collagen; D017474:Receptors, Laminin / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013154:Spleen / Q000378:metabolism; D014407:Tumor Cells, Cultured
D005353:Fibronectins; D016023:Integrins; D007797:Laminin; D009842:Oligopeptides; D038981:Receptors, Collagen; D017474:Receptors, Laminin; D003094:Collagen