Intramolecular interactions in vinculin control α‐actinin binding to the vinculin head

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Abstract
Using blot overlay techniques we have investigated the interaction of vinculin with α‐actinin. We show that an α‐actinin binding site is located in the 90 kDa vinculin head and confirm a vinculin binding site in the C‐terminal rod of α‐actinin, as recently reported by McGregor et al. [(1994) Biochem. J. 310, 225–233]. The isolated vinculin head binds much more strongly to α‐actinin than intact vinculin. Using a proteolytic 81 kDa head fragment, we show that vinculin residues 1–107 are required for α‐actinin binding. Antibodies directed against vinculin residues 808–850 inhibit the vinculin‐α‐actinin binding, suggesting that this sequence is directly involved in, or topographically related to, the α‐actinin binding site.