1f2p
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CRYSTAL STRUCTURE OF THE STREPTOMYCES GRISEUS AMINOPEPTIDASE COMPLEXED WITH L-PHENYLALANINE
OverviewOverview
Streptomyces griseus aminopeptidase (SGAP) is a double-zinc exopeptidase, with a high preference toward large hydrophobic amino-terminus residues., It is a monomer of a relatively low molecular weight (30 kDa), it is heat, stable, it displays a high and efficient catalytic turnover, and its, activity is modulated by calcium ions. The small size, high activity, and, heat stability make SGAP a very attractive enzyme for various, biotechnological applications, among which is the processing of, recombinant DNA proteins and fusion protein products. Several free amino, acids, such as phenylalanine, leucine, and methionine, were found to act, as weak inhibitors of SGAP and hence were chosen for structural studies., These inhibitors can potentially be regarded as product analogs because, one of the products obtained in a normal enzymatic reaction is the cleaved, amino terminal amino acid of the substrate. The current study includes the, X-ray crystallographic analysis of the SGAP complexes with methionine, (1.53 A resolution), leucine (1.70 A resolution), and phenylalanine (1.80, A resolution). These three high-resolution structures have been used to, fully characterize the SGAP active site and to identify some of the, functional groups of the enzyme that are involved in enzyme-substrate and, enzyme-product interactions. A unique binding site for the terminal amine, group of the substrate (including the side chains of Glu131 and Asp160, as, well as the carbonyl group of Arg202) is indicated to play an important, role in the binding and orientation of both the substrate and the product, of the catalytic reaction. These studies also suggest that Glu131 and, Tyr246 are directly involved in the catalytic mechanism of the enzyme., Both of these residues seem to be important for substrate binding and, orientation, as well as the stabilization of the tetrahedral transition, state of the enzyme-substrate complex. Glu131 is specifically suggested to, function as a general base during catalysis by promoting the nucleophilic, attack of the zinc-bound water/hydroxide on the substrate carbonyl carbon., The structures of the three SGAP complexes are compared with recent, structures of three related aminopeptidases: Aeromonas proteolytica, aminopeptidase (AAP), leucine aminopeptidase (LAP), and methionine, aminopeptidase (MAP) and their complexes with corresponding inhibitors and, analogs. These structural results have been used for the simulation of, several species along the reaction coordinate and for the suggestion of a, general scheme for the proteolytic reaction catalyzed by SGAP.
About this StructureAbout this Structure
1F2P is a Single protein structure of sequence from Streptomyces chryseus with ZN, CA and PHE as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Interactions of Streptomyces griseus aminopeptidase with amino acid reaction products and their implications toward a catalytic mechanism., Gilboa R, Spungin-Bialik A, Wohlfahrt G, Schomburg D, Blumberg S, Shoham G, Proteins. 2001 Sep 1;44(4):490-504. PMID:11484227
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