6cpa
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(New page: 200px<br /><applet load="6cpa" size="450" color="white" frame="true" align="right" spinBox="true" caption="6cpa, resolution 2.0Å" /> '''CRYSTAL STRUCTURE OF ...)
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Revision as of 13:23, 20 November 2007
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CRYSTAL STRUCTURE OF THE COMPLEX OF CARBOXYPEPTIDASE A WITH A STRONGLY BOUND PHOSPHONATE IN A NEW CRYSTALLINE FORM: COMPARISON WITH STRUCTURES OF OTHER COMPLEXES
Overview
O-[[(1R)-[[N-(Phenylmethoxycarbonyl)-L-alanyl]amino]ethyl], hydroxyphosphinyl]-L-3-phenyllacetate [ZAAP(O)F], an analogue of, (benzyloxycarbonyl)-Ala-Ala-Phe or, (benzyloxycarbonyl)-Ala-Ala-phenyllactate, binds to carboxypeptidase A, with great affinity (Ki = 3 pM). Similar phosphonates have been shown to, be transition-state analogues of the CPA-catalyzed hydrolysis [Hanson, J., E., Kaplan, A. P., & Bartlett, P. A. (1989) Biochemistry 28, 6294-6305]., In the present study, the structure of the complex of this phosphonate, with carboxypeptidase A has been determined by X-ray crystallography to a, resolution of 2.0 A. The complex crystallizes in the space group, P2(1)2(1)2(1) with cell dimensions a = 61.9 A, b = 67.2 A, and c = 76.2 A., The structure of the complex was solved by molecular replacement., Refinement of the structure against 20,776 unique reflections between 10.0, and 2.0 A yields a crystallographic residual of 0.193, including 140 water, molecules. The two phosphinyl oxygens of the inhibitor bind to the, active-site zinc at 2.2 A on the electrophilic (Arg-127) side and 3.1 A on, the nucleophilic (Glu-270) side. Various features of the binding mode of, this phosphonate inhibitor are consistent with the hypothesis that, carboxypeptidase A catalyzed hydrolysis proceeds through a general-base, mechanism in which the carbonyl carbon of the substrate is attacked by, Zn-hydroxyl (or Zn-water). An unexpected feature of the bound inhibitor, the cis carbamoyl ester bond at the benzyloxycarbonyl linkage to alanine, allows the benzyloxycarbonyl phenyl ring of the inhibitor to interact, favorably with Tyr-198. This complex structure is compared with previous, structures of carboxypeptidase A, including the complexes with the potato, inhibitor, a hydrated keto methylene substrate analogue, and a, phosphonamidate inhibitor. Comparisons are also made with the complexes of, thermolysin with some phosphonamidate inhibitors.
About this Structure
6CPA is a Single protein structure of sequence from Bos taurus with ZN and ZAF as ligands. Active as Carboxypeptidase A, with EC number 3.4.17.1 Full crystallographic information is available from OCA.
Reference
Crystal structure of the complex of carboxypeptidase A with a strongly bound phosphonate in a new crystalline form: comparison with structures of other complexes., Kim H, Lipscomb WN, Biochemistry. 1990 Jun 12;29(23):5546-55. PMID:2386784
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