Inhibition of carboxypeptidase A by excess zinc: analysis of the structural determinants by X-ray crystallography.

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作者：

M Gomez-Ortiz，FX Gomis-Rüth，R Huber，FX Avilés

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摘要：

Pancreatic metallocarboxypeptidases are inhibited by a millimolar excess of zinc together with other exo- and endometalloproteases. We have analyzed the structure of bovine carboxypeptidase A inhibited by an excess of zinc ions using X-ray crystallography at 1.7 A overall resolution. Under these conditions, a second zinc is observed to bind to the enzyme active site, establishing a distorted tetrahedrally coordinated complex which involves Glu-270 (the general base for catalysis), a water molecule, a chloride ion, and a hydroxide ion. This hydroxide ion forms a 114 degrees angular bridge between the inhibitory and the catalytic zinc ions, which are at a distance of 3.3 A from one another. The inhibitory zinc holds the hydroxide at nearly the same location as a previously observed active site water molecule (W571) and probably perturbs the substrate positioning and stereochemical rearrangements required for substrate cleavage during catalysis.

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关键词：

Animals Cattle Zinc Carboxypeptidases Carboxypeptidases A Crystallography, X-Ray Protein Conformation Binding Sites Molecular Sequence Data Catalysis