4mat
E.COLI METHIONINE AMINOPEPTIDASE HIS79ALA MUTANT
Structural highlights
FunctionMAP1_ECOLI Removes the N-terminal methionine from nascent proteins. The N-terminal methionine is often cleaved when the second residue in the primary sequence is small and uncharged (Met-Ala-, Cys, Gly, Pro, Ser, Thr, or Val). Requires deformylation of the N(alpha)-formylated initiator methionine before it can be hydrolyzed.[HAMAP-Rule:MF_01974][1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBy 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. 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[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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