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| [[Image:1df0.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_1df0| PDB=1df0 | SCENE= }} | | {{STRUCTURE_1df0| PDB=1df0 | SCENE= }} |
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| '''CRYSTAL STRUCTURE OF M-CALPAIN'''
| | ===CRYSTAL STRUCTURE OF M-CALPAIN=== |
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| ==Overview==
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| 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.
| | The line below this paragraph, {{ABSTRACT_PUBMED_10601010}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 10601010 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_10601010}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Zymogen]] | | [[Category: Zymogen]] |
| [[Category: Zymogen activation]] | | [[Category: Zymogen activation]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 13:46:38 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 22:55:40 2008'' |