Zinc Environment and cis Peptide Bonds in Carboxypeptidase A at 1.75Å Resolution
| Autor: | K. D. Hardman, Richard B. Honzatko, Douglas C. Rees, M. Lewis, William N. Lipscomb |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 1981 |
| Předmět: |
Carboxypeptidases A
Protein Conformation Stereochemistry chemistry.chemical_element Carboxypeptidases Zinc Ligands Catalysis chemistry.chemical_compound X-Ray Diffraction Hydrolase Animals Organic chemistry Peptide bond Binding Sites Multidisciplinary Dipeptide biology Chemistry Ligand Water Active site Dipeptides Carboxypeptidase biology.protein Carboxypeptidase A Cattle Peptides Research Article |
| Popis: | The structure of the metalloenzyme carboxypeptidase A (peptidyl-L-amino-acid hydrolase, EC 3.4.17.1) has been refined at 1.75 A by a restrained least-squares procedure to a conventional crystallographic R factor of 0.162. Significant results of the refined structure relative to the catalytic mechanism are described. In the native enzyme, the zinc coordination number is five (two imidazole N delta 1 nitrogens, the two carboxylate oxygens of glutamate-72, and a water molecule). In the complex (at 2.0-A resolution) of carboxypeptidase A with the dipeptide glycyl-L-tyrosine, however, the water ligand is replaced by both the carbonyl oxygen and the amino nitrogen of the dipeptide. The amino nitrogen also statistically occupies a second position near glutamate-270. Consequently, the coordination number of zinc may vary from five to six in carboxypeptidase A-substrate complexes. Implications of these results for the catalytic mechanism of carboxypeptidase A are discussed. In addition, three cis peptide bonds, none of which involves proline as the amino nitrogen donor, have been located fairly near the active site. |
| Databáze: | OpenAIRE |
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