5tmp
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(New page: 200px<br /><applet load="5tmp" size="450" color="white" frame="true" align="right" spinBox="true" caption="5tmp, resolution 1.98Å" /> '''COMPLEX OF E. COLI T...)
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COMPLEX OF E. COLI THYMIDYLATE KINASE WITH THE BISUBSTRATE INHIBITOR AZTP5A
Overview
The crystal structures of Escherichia coli thymidylate kinase (TmpK) in, complex with P1-(5'-adenosyl)-P5-(5'-thymidyl)pentaphosphate and, P1-(5'-adenosyl)P5-[5'-(3'-azido-3'-deoxythymidine)] pentaphosphate have, been solved to 2.0-A and 2.2-A resolution, respectively. The overall, structure of the bacterial TmpK is very similar to that of yeast TmpK. In, contrast to the human and yeast TmpKs, which phosphorylate, 3'-azido-3'-deoxythymidine 5'-monophosphate (AZT-MP) at a 200-fold reduced, turnover number (kcat) in comparison to the physiological substrate dTMP, reduction of kcat is only 2-fold for the bacterial enzyme. The different, kinetic properties toward AZT-MP between the eukaryotic TmpKs and E. coli, TmpK can be rationalized by the different ways in which these enzymes, stabilize the presumed transition state and the different manner in which, a carboxylic acid side chain in the P loop interacts with the deoxyribose, of the monophosphate. Yeast TmpK interacts with the 3'-hydroxyl of dTMP, through Asp-14 of the P loop in a bidentate manner: binding of AZT-MP, results in a shift of the P loop to accommodate the larger substituent. In, E. coli TmpK, the corresponding residue is Glu-12, and it interacts in a, side-on fashion with the 3'-hydroxyl of dTMP. This different mode of, interaction between the P loop carboxylic acid with the 3' substituent of, the monophosphate deoxyribose allows the accommodation of an azido group, in the case of the E. coli enzyme without significant P loop movement. In, addition, although the yeast enzyme uses Arg-15 (a glycine in E. coli) to, stabilize the transition state, E. coli seems to use Arg-153 from a region, termed Lid instead. Thus, the binding of AZT-MP to the yeast TmpK results, in the shift of a catalytic residue, which is not the case for the, bacterial kinase.
About this Structure
5TMP is a Single protein structure of sequence from Escherichia coli with Z5A as ligand. Active as dTMP kinase, with EC number 2.7.4.9 Full crystallographic information is available from OCA.
Reference
Structural basis for efficient phosphorylation of 3'-azidothymidine monophosphate by Escherichia coli thymidylate kinase., Lavie A, Ostermann N, Brundiers R, Goody RS, Reinstein J, Konrad M, Schlichting I, Proc Natl Acad Sci U S A. 1998 Nov 24;95(24):14045-50. PMID:9826650
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