A point mutation in a highly conserved region of the β1 subunit, Asp130 to Ala (D130A) substitution, abrogates the Arg-Gly-Asp (RGD)-dependent binding of α5β1 to fibronectin (FN) without disrupting gross structure or heterodimer assembly. The D130A mutation also interferes with binding to invasin, a ligand that lacks RGD sequence. In spite of the lack of detectable FN binding by α5β1(D130A), it was recruited to adhesion plaques formed on FN by endogenous hamster receptors. Thus, intact ligand binding function is not required for recruitment of α5β1 to adhesion plaques. Overexpression of β1(D130A) partially interfered with endogenous α5β1 function, thus defining a dominant negative β1 integrin mutation.
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