title: Crystal structure of vinculin in complex with vinculin binding site 50 (VBS50), the integrin binding site 2 (IBS2) of talin.
abstract: The cytoskeletal protein talin activates integrin receptors by binding of its FERM domain to the cytoplasmic tail of β-integrin. Talin also couples integrins to the actin cytoskeleton, largely by binding to and activating the cytoskeletal protein vinculin, which binds to F-actin through the agency of its five-helix bundle tail (Vt) domain. Talin activates vinculin by means of buried amphipathic α-helices coined vinculin binding sites (VBSs) that reside within numerous four- and five-helix bundle domains that comprise the central talin rod, which are released from their buried locales by means of mechanical tension on the integrin:talin complex. In turn, these VBSs bind to the N-terminal seven-helix bundle (Vh1) domain of vinculin, creating an entirely new helix bundle that severs its head-tail interactions. Interestingly, talin harbors a second integrin binding site coined IBS2 that consists of two five-helix bundle domains that also contain a VBS (VBS50). Here we report the crystal structure of VBS50 in complex with vinculin at 2.3 Å resolution and show that intramolecular interactions of VBS50 within IBS2 are much more extensive versus its interactions with vinculin. Indeed, the IBS2-vinculin interaction only occurs at physiological temperature and the affinity of VBS50 for vinculin is about 30 times less than other VBSs. The data support a model where integrin binding destabilizes IBS2 to allow it to bind to vinculin.
authors.affiliation: Department of Cancer Biology, Cell Adhesion Laboratory, The Scripps Research Institute, Jupiter, Florida 33458, USA.
authors.forename: S D
authors.initials: SD
authors.lastname: Yogesha
authors.forename: Erumbi S
authors.initials: ES
authors.lastname: Rangarajan
authors.forename: Clemens
authors.initials: C
authors.lastname: Vonrhein
authors.forename: Gerard
authors.initials: G
authors.lastname: Bricogne
authors.forename: Tina
authors.initials: T
authors.lastname: Izard
mesh_terms: D000199:Actins / Q000737:chemistry*; D001665:Binding Sites; D002151:Calorimetry; D022001:Focal Adhesions / Q000737:chemistry; D006801:Humans; D016023:Integrins / Q000737:chemistry*; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000737:chemistry; D016608:Talin / Q000737:chemistry*; D016596:Vinculin / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D000199:Actins; D016023:Integrins; D046912:Multiprotein Complexes; D011956:Receptors, Cell Surface; D016608:Talin; C488955:VCL protein, human; D016596:Vinculin