1blc: Difference between revisions

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

Crystallographic studies of the complex between beta-lactamase and clavulanate reveal a structure of two acyl-enzymes with covalent bonds at the active site Ser70, representing two different stages of inhibitor degradation alternately occupying the active site. Models that are consistent with biochemical data are derived from the electron density map and refined at 2.2 A resolution: cis enamine, in which the carboxylate group of the clavulanate molecule makes a salt bridge with Lys234 of beta-lactamase; decarboxylated trans enamine, which is oriented away from Lys234. For both acyl-enzymes, the carbonyl oxygen atom of the ester group occupies the oxyanion hole in a manner similar to that found in inhibitor binding to serine proteases. Whereas the oxygen atom in the trans product is optimally positioned in the oxyanion hole, that of the cis product clashes with the main-chain nitrogen atom of Ser70 and the beta-carbon atom of the adjacent Ala69. In contrast to cis to trans isomerization in solution that relieves the steric strain inherent in a cis double bond, at the enzyme-inhibitor interface two additional factors play an important role. The salt bridge enhances the stability of the cis product, while the steric strain introduced by the short contacts with the protein reduces its stability.

1BLC is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Staphylococcus_aureus Staphylococcus aureus] with <scene name='pdbligand=SO4:'>SO4</scene> and <scene name='pdbligand=CEM:'>CEM</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Beta-lactamase Beta-lactamase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.5.2.6 3.5.2.6] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1BLC OCA].  

[[Category: Chen, C C.H.]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 11:56:33 2008''