PMID: 22394450
Koch M, Fritz G
The Structure of Ca(2+) -loaded S100A2 at 1.3 A resolution.
FEBS J. 2012 Mar 6. doi: 10.1111/j.1742-4658.2012.08556.x.
S100A2 is an EF-hand Ca(2+) -binding protein that activates the tumor suppressor p53. In order to understand the molecular mechanisms underlying the Ca(2+) -induced activation of S100A2 the structure of Ca(2+) -bound S100A2 was determined at 1.3 A resolution by X-ray crystallography. The structure was compared to Ca(2+) -free S100A2 and to other S100 proteins. Ca(2+) binding to S100A2 induces small structural changes in the N-terminal EF-hand, but a large conformational change in the C-terminal EF-hand reorienting helix III by approximately 90 degrees is observed. This movement is accompanied by the exposure of a hydrophobic cavity between helix III and helix IV that represents the target protein interaction site. This molecular reorganization is associated with the breaking and new formation of intramolecular hydrophobic contacts. The target binding site exhibits unique features; in particular the hydrophobic cavity is larger than in other Ca(2+) -loaded S100 proteins. The structural data underline that the shape and size of the hydrophobic cavity are major determinants for target specificity of S100 proteins and suggests that the binding mode for S100A2 is different from other p53-interacting S100 proteins. STRUCTURED DIGITAL ABSTRACT: S100A2 and S100A2bind by x-ray crystallography (View interaction).