Regulation and Function of Ligand Binding Sites in Talin

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Talin is an essential component of cell-matrix adherens type junctions (focal adhesions, FA). Dynamic modulation of ligand binding to talin has been implicated in the control of both the mechanical stability and the turnover of the intracellular adhesion complex. Regulation of ligand binding sites in talin, however, is not characterized sufficiently. This proposed work will provide a detailed investigation of the interdependence of binding site activities in a C-terminal domain construct of talin, termed talinC. Ligand binding of talinC conveys FA targeting of the protein in cells and allows investigation of vinculin interaction with high affinity interaction sites (VBS). In purified talinC, the VBS helices are concealed in its bundled domain structure. Activation of talinC VBS helices in FAs is supposed to involve integrin and F-actin binding. This work uses selective binding site mutants in conjunction with FRAP- and FRET-based analysis of fluorescently labelled protein to reveal the dynamic association of talinC variants with and conformational rearrangements in FAs. The work will provide novel insight in the intricate regulation of ligand binding and its connection to a supposed mechano-sensor function of talinC and, furthermore, contribute to a molecular understanding of the regulation of binding site in talin.