Interaction of type IV collagen with the isolated integrins alpha 1 beta 1 and alpha 2 beta 1.
The triple-helical cyanogen-bromide-derived fragment CB3[IV] of collagen IV, located 100 nm from the N-terminus of the molecule, contains the binding sites for the integrins alpha 1 beta 1 and alpha 2 beta 1. To investigate the interaction of these integrins and collagen IV, we performed solid-phase and inhibition assays using as receptor isolated alpha 1 beta 1 and alpha 2 beta 1. The ligands used were the binding-site-bearing trimeric peptide CB3[IV] and its shorter tryptic fragments F1-F4. Using titration curves, in which the binding of soluble receptors to coated ligands and the binding of soluble ligands to coated receptors were analyzed, the binding sites for alpha 1 beta 1 and alpha 2 beta 1 were in different but adjacent areas of CB3[IV]. Triple-helical conformation and distinct primary structures were required for the interaction. Dissociation constants (Kd), for the affinity of integrins for collagen IV, were determined in the 1-nM range in the presence of Mn2+ and Mg2+. In the absence of Mn2+, the Kd values indicated a 30-60-fold decrease in the affinities, which for alpha 2 beta 1 was further reduced by adding Ca2+. In the presence of Ca2+ and Mg2+ the affinity of collagen IV for alpha 1 beta 1 was four-times higher than for alpha 2 beta 1.
Kern
A
A
Max-Planck-Institut für Biochemie, Martinsried, Germany.
Eble
J
J
Golbik
R
R
Kühn
K
K
D000595:Amino Acid Sequence; D001665:Binding Sites; D003094:Collagen / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary
D016023:Integrins; D003094:Collagen