Biomedical subjects

Gerard Bricogne

Publications and source records attributed to Gerard Bricogne.

3 recordsLinked to original sources

PubMed2004

Crystal structure of human vinculin.

Alterations in the actin cytoskeleton following the formation of cell-matrix and cell-cell junctions are orchestrated by vinculin. Vinculin associates with a large number of cytoskeletal and signaling proteins, and this flexibility is thought to contribute to rapid dissociation and reassociations of adhesion complexes. Intramolecular interactions between vinculin's head (Vh) and tail (Vt) domains limit access of its binding sites for other adhesion proteins. While the crystal structures of the Vh and Vt domains are known, these domains represent less than half of the entire protein and are separated by a large central region of unknown structure and function. Here we report the crystal structure of human full-length vinculin to 2.85 A resolution. In its resting state, vinculin is a loosely packed collection of alpha-helical bundles held together by Vh-Vt interactions. The three new well ordered alpha-helical bundle domains are similar in their structure to either Vh (Vh2 and Vh3) or to Vt (Vt2) and their loose packing provides the necessary flexibility that allows vinculin to interact with its various protein partners at sites of cell adhesion.

Animals↗

PubMed2004

Solving the structure of the bubble protein using the anomalous sulfur signal from single-crystal in-house Cu Kalpha diffraction data only.

A small cysteine-rich protein, the function of which remains elusive, was discovered in the exudate of a Penicillium species. Crystal diffraction experiments conducted using in-house Cu Kalpha radiation and an R-AXIS IV++ imaging-plate detector yielded high-quality data to 1.4 A, with a distinguishable anomalous signal from sulfur (DeltaF/F = 0.031). This was used to phase the data and solve the structure using a single data set; the 64-residue amino-acid sequence was unambiguously determined from the electron density. It revealed a globular all-beta protein with a hitherto unknown fold, having a surface electrostatic charge distribution that is similar to that of another small secreted fungal protein, the Williopsis mrakii killer toxin. Aligning the charge distribution superimposed the potential recognition sites of the two proteins, suggesting a similar negatively charged target.

Amino Acid Sequence↗

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↗