1qxp: Difference between revisions

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

The two Ca2+-dependent cysteine proteases, micro- and m-calpain, are involved in various Ca2+-linked signal pathways but differ markedly in their Ca2+ requirements for activation. We have determined the structure of a micro-like calpain, which has 85% micro-calpain sequence (the first 48 and the last 62 residues of the large subunit are those from m-calpain) and a low Ca2+ requirement. This construct was used because micro-calpain itself is too poorly expressed. The structure of micro-like calpain is very similar in overall fold to that of m-calpain as expected, but differs significantly in two aspects. In comparison with m-calpain, the catalytic triad residues in micro-like calpain, His and Cys, are much closer together in the absence of Ca2+, and significant portions of the Ca2+ binding EF-hand motifs are disordered and more flexible. These structural differences imply that Ca2+-free micro-calpain may represent a partially activated structure, requiring lower Ca2+ concentration to trigger its activation.

1QXP is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Rattus_norvegicus Rattus norvegicus]. Active as [http://en.wikipedia.org/wiki/Calpain-1 Calpain-1], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.22.52 3.4.22.52] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1QXP OCA].  

[[Category: Elce, J S.]]

[[Category: Pal, G P.]]

[[Category: Veyra, T D.]]

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