Direct evidence of vinculin tail–lipid membrane interaction in beta-sheet conformation

The focal adhesion protein vinculin (1066 residues) plays an important role in cell adhesion and migration. The interaction between vinculin and lipid membranes is necessary to ensure these processes. There are three putative lipid-membrane interaction sites located at the vinculin tail domain two that form amphipathic alpha-helices (residues 935–978 and 1020–1040) and one that remains unstructured (residues 1052–1066) during crystallization. In this work, the structural and biochemical properties of the last 21 residues of the vinculin tail domain were investigated. Differential scanning calorimetry was performed in the presence of lipid vesicles consisting of dimyristoyl-l-α-phosphatidylcholine and dimyristoyl-l-α-phosphatidylglycerol at various molar ratios. The results demonstrate that this peptide inserts into lipid vesicle membranes. Examining the secondary structure of this peptide by molecular dynamics simulations and circular dichroism spectroscopy, we show that it adopts an antiparallel beta sheet backbone geometry that could ensure the association with lipid vesicles.