4ape: Difference between revisions

The active site of the aspartic proteinase, endothiapepsin, has been defined by X-ray analysis and restrained least-squares refinement at 2.1 A resolution with a crystallographic agreement value of 0.16. The environments of the two catalytically important aspartyl groups are remarkably similar and the contributions of the NH2- and COOH-terminal domains to the catalytic centre are related by a local 2-fold axis. The carboxylates of the aspartyls share a hydrogen bond and have equivalent contacts to a bound water molecule or hydroxonium ion lying on the local diad. The main chains around 32 and 215 are connected by a novel interaction involving diad-related threonines. It is suggested that the two pKa values of the active site aspartyls arise from a structure not unlike that in maleic acid with a hydrogen-bonded intermediate species and a dicarboxylate characterised by electrostatic repulsions between the two negatively charged groups.

4APE is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Cryphonectria_parasitica Cryphonectria parasitica]. This structure supersedes the now removed PDB entries 2APE and 1APE. The following page contains interesting information on the relation of 4APE with [[http://pdb.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb12_1.html Pepsin]]. Active as [http://en.wikipedia.org/wiki/Endothiapepsin Endothiapepsin], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.23.22 3.4.23.22] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4APE OCA].  

[[Category: Blundell, T L.]]

[[Category: Cooper, J B.]]

[[Category: Jenkins, J A.]]

[[Category: Pearl, L H.]]

[[Category: Sewell, B T.]]

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