3cpa
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(New page: 200px<br /><applet load="3cpa" size="450" color="white" frame="true" align="right" spinBox="true" caption="3cpa, resolution 2.0Å" /> '''X-RAY CRYSTALLOGRAPHI...)
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Revision as of 17:29, 20 November 2007
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X-RAY CRYSTALLOGRAPHIC INVESTIGATION OF SUBSTRATE BINDING TO CARBOXYPEPTIDASE A AT SUBZERO TEMPERATURE
Overview
A high-resolution x-ray crystallographic investigation of the complex, between carboxypeptidase A (CPA; peptidyl-L-amino-acid hydrolase, EC, 3.4.17.1) and the slowly hydrolyzed substrate glycyl-L-tyrosine was done, at -9 degrees C. Although this enzyme-substrate complex has been the, subject of earlier crystallographic investigation, a higher resolution, electron-density map of the complex with greater occupancy of the, substrate was desired. All crystal chemistry (i.e., crystal soaking and, x-ray data collection) was performed on a diffractometer-mounted flow, cell, in which the crystal was immobilized. The x-ray data to 1.6-A, resolution have yielded a well-resolved structure in which the zinc ion of, the active site is five-coordinate: three enzyme residues (glutamate-72, histidine-69, and histidine-196) and the carbonyl oxygen and amino, terminus of glycyl-L-tyrosine complete the coordination polyhedron of the, metal. These results confirm that this substrate may be bound in a, nonproductive manner, because the hydrolytically important zinc-bound, water has been displaced and excluded from the active site. It is likely, that all dipeptide substrates of carboxypeptidase A that carry an, unprotected amino terminus are poor substrates because of such favorable, bidentate coordination to the metal ion of the active site.
About this Structure
3CPA is a Single protein structure of sequence from [1] with ZN as ligand. This structure superseeds the now removed PDB entry 1CPA. Active as Carboxypeptidase A, with EC number 3.4.17.1 Full crystallographic information is available from OCA.
Reference
X-ray crystallographic investigation of substrate binding to carboxypeptidase A at subzero temperature., Christianson DW, Lipscomb WN, Proc Natl Acad Sci U S A. 1986 Oct;83(20):7568-72. PMID:3463986
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