2mat
E.COLI METHIONINE AMINOPEPTIDASE AT 1.9 ANGSTROM RESOLUTION
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OverviewOverview
By improving the expression and purification of Escherichia coli, methionine aminopeptidase (eMetAP) and using slightly different, crystallization conditions, the resolution of the parent structure was, extended from 2.4 to 1.9 A resolution. This has permitted visualization of, the coordination geometry and solvent structure of the active-site, dinuclear metal center. One solvent molecule (likely a mu-hydroxide), bridges the trigonal bipyramidal (Co1) and octahedral (Co2) cobalt ions. A, second solvent (possibly a hydroxide ion) is bound terminally to Co2. A, monovalent cation binding site was also identified about 13 A away from, the metal center at an interface between the two subdomains of the, protein. The first structure of a substrate-like inhibitor, (3R)-amino-(2S)-hydroxyheptanoyl-L-Ala-L-Leu-L-Val-L-Phe-OMe, bound to a, methionine aminopeptidase, has also been determined. This inhibitor, coordinates the metal center through four interactions as follows: (i), ligation of the N-terminal (3R)-nitrogen to Co2, (ii, iii) bridging, coordination of the (2S)-hydroxyl group, and (iv) terminal ligation to Co1, by the keto oxygen of the pseudo-peptide linkage. Inhibitor binding occurs, with the displacement of two solvent ligands and the expansion of the, coordination sphere of Co1. In addition to the tetradentate, bis-chelate, metal coordination, the substrate analogue forms hydrogen bonds with His79, and His178, two conserved residues within the active site of all MetAPs., To evaluate their importance in catalysis His79 and His178 were replaced, with alanine. Both substitutions, but especially that of His79, reduce, activity. The structure of the His79Ala apoenzyme and the comparison of, its electronic absorption spectra with other variants suggest that the, loss in activity is not due to a conformational change or a defective, metal center. Two different reaction mechanisms are proposed and are, compared to those of related enzymes. These results also suggest that, inhibitors analogous to that reported here may be useful in preventing, angiogenesis in cancer and in the treatment of microbial and fungal, infections.
About this StructureAbout this Structure
2MAT is a Single protein structure of sequence from Escherichia coli with CO and NA as ligands. Active as Methionyl aminopeptidase, with EC number 3.4.11.18 Full crystallographic information is available from OCA.
ReferenceReference
Escherichia coli methionine aminopeptidase: implications of crystallographic analyses of the native, mutant, and inhibited enzymes for the mechanism of catalysis., Lowther WT, Orville AM, Madden DT, Lim S, Rich DH, Matthews BW, Biochemistry. 1999 Jun 15;38(24):7678-88. PMID:10387007
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