1df0: Difference between revisions

[[Image:1df0.gif|left|200px]]<br /><applet load="1df0" size="350" color="white" frame="true" align="right" spinBox="true"  

The combination of thiol protease activity and calmodulin-like EF-hands is a feature unique to the calpains. The regulatory mechanisms governing calpain activity are complex, and the nature of the Ca(2+)-induced switch between inactive and active forms has remained elusive in the absence of structural information. We describe here the 2.6 A crystal structure of m-calpain in the Ca(2+)-free form, which illustrates the structural basis for the inactivity of calpain in the absence of Ca(2+). It also reveals an unusual thiol protease fold, which is associated with Ca(2+)-binding domains through heterodimerization and a C(2)-like beta-sandwich domain. Strikingly, the structure shows that the catalytic triad is not assembled, indicating that Ca(2+)-binding must induce conformational changes that re-orient the protease domains to form a functional active site. The alpha-helical N-terminal anchor of the catalytic subunit does not occupy the active site but inhibits its assembly and regulates Ca(2+)-sensitivity through association with the regulatory subunit. This Ca(2+)-dependent activation mechanism is clearly distinct from those of classical proteases.

1DF0 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Rattus_norvegicus Rattus norvegicus]. Active as [http://en.wikipedia.org/wiki/Hydrolase Hydrolase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.22.52 and 3.4.22.53 3.4.22.52 and 3.4.22.53] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1DF0 OCA].  

[[Category: Davies, P L.]]

[[Category: Elce, J S.]]

[[Category: Hosfield, C M.]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:15:57 2008''