Paper Report for: Rees_1981_Proc.Natl.Acad.Sci.U.S.A_78_3408
Reference
Title: Zinc environment and cis peptide bonds in carboxypeptidase A at 1.75-A resolution Rees DC, Lewis M, Honzatko RB, Lipscomb WN, Hardman KD Ref: Proceedings of the National Academy of Sciences of the United States of America, 78:3408, 1981 : PubMed
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.
        
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Rees DC, Lewis M, Honzatko RB, Lipscomb WN, Hardman KD (1981) Zinc environment and cis peptide bonds in carboxypeptidase A at 1.75-A resolution Proceedings of the National Academy of Sciences of the United States of America78: 3408-12
Rees DC, Lewis M, Honzatko RB, Lipscomb WN, Hardman KD (1981) Proceedings of the National Academy of Sciences of the United States of America78: 3408-12