Chemical cross-linking leads to two high molecular mass aggregates of rat alpha 1 beta 1 integrin differing in their conformation but not in their composition.
In order to detect protein interactions of the collagen/laminin receptor alpha 1 beta 1 integrin, covalent chemical cross-linking was performed with the homo-bifunctional, amine reactive reagents DSS (disuccinimidylsuberate) and DSP (dithiobis(succinimidylpropionate)). After cross-linking of the 190 kDa rat alpha 1 integrin subunit, immunoblotting revealed two additional, immunoreactive, high molecular mass complexes (M(r) 240/290 k). Generation of the 240/290 kDa aggregates depended on the presence of the intact tertiary protein structure. As shown with immunoaffinity purified proteins, the 240/290 kDa aggregates consist exclusively of alpha 1 and beta 1 integrin subunits. No other cross-linked proteins associated with the alpha 1 or beta 1 subunit were detected. In contrast to the non-cross-linkable alpha 1 beta 1 integrin, the 240/290 kDa aggregates presumably represent active forms of the adhesion receptor, because both bound in vitro to collagen I and IV. This ability of alpha 1 beta 1 integrin to cross-link and produce two additional high molecular mass forms is shared by rat alpha 9 beta 1 integrin. Thus, the cross-linking approach directly indicates that beta 1 integrins occur in different conformations caused by variations in the folding and/or spatial arrangement of their subunits.
Löster
K
K
Institut für Molekularbiologie und Biochemie, Freie Universität Berlin, Germany.
Baum
O
O
Hofmann
W
W
Reutter
W
W
D000818:Animals; D002462:Cell Membrane / Q000737:chemistry; D002846:Chromatography, Affinity; D003094:Collagen / Q000378:metabolism; D003432:Cross-Linking Reagents; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry; D004229:Dithiothreitol; D015151:Immunoblotting; D039222:Integrin alpha1beta1; D016023:Integrins / Q000737:chemistry* / Q000378:metabolism; D008099:Liver / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry; D008970:Molecular Weight; D017830:Octoxynol; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D051381:Rats; D013388:Succinimides
D003432:Cross-Linking Reagents; D004220:Disulfides; D039222:Integrin alpha1beta1; D016023:Integrins; D008565:Membrane Proteins; D013388:Succinimides; D017830:Octoxynol; D003094:Collagen; D018819:Dipeptidyl Peptidase 4; C011240:dithiobis(succinimidylpropionate); D004229:Dithiothreitol; C019358:disuccinimidyl suberate