Christina L Rush | PubMed Health

PubMed2004

Rhombohedral crystals of the human vinculin head domain in complex with a vinculin-binding site of talin.

Intermolecular interactions between the cytoskeletal proteins talin and vinculin are required for outside-in integrin signaling triggered by the formation of focal adhesions. Talin possesses three non-contiguous vinculin-binding sites (VBS); binding of one of these motifs, VBS3, provokes dramatic alterations in the structure of the vinculin's head (Vh) domain and this activates vinculin (Izard et al., 2004). To address the role of talin's other VBSs in vinculin activation, talin VBS1 (human residues 607-636) was crystallized in complex with the Vh (human residues 1-258) domain. Rhombohedral crystals of human Vh-VBS1 were obtained. The crystals belong to space group R32, with unit-cell parameters a = 88.7 A, alpha = 105.5 degrees and diffract to 2.4 A on a third-generation synchrotron source. The packing density for one heterodimer in the asymmetric unit is 3.04 A(3) Da(-1), with a solvent content of 0.59.

Binding Sites↗

PubMed2003

Vinculin activation by talin through helical bundle conversion.

Vinculin is a conserved component and an essential regulator of both cell-cell (cadherin-mediated) and cell-matrix (integrin-talin-mediated focal adhesions) junctions, and it anchors these adhesion complexes to the actin cytoskeleton by binding to talin in integrin complexes or to alpha-actinin in cadherin junctions. In its resting state, vinculin is held in a closed conformation through interactions between its head (Vh) and tail (Vt) domains. The binding of vinculin to focal adhesions requires its association with talin. Here we report the crystal structures of human vinculin in its inactive and talin-activated states. Talin binding induces marked conformational changes in Vh, creating a novel helical bundle structure, and this alteration actively displaces Vt from Vh. These results, as well as the ability of alpha-actinin to also bind to Vh and displace Vt from pre-existing Vh-Vt complexes, support a model whereby Vh functions as a domain that undergoes marked structural changes that allow vinculin to direct cytoskeletal assembly in focal adhesions and adherens junctions. Notably, talin's effects on Vh structure establish helical bundle conversion as a signalling mechanism by which proteins direct cellular responses.

Adherens Junctions↗