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Structure of Aes from E. coli in covalent complex with PMS
Structural highlights
FunctionAES_ECOLI Displays esterase activity towards short chain fatty esters (acyl chain length of up to 8 carbons). Able to hydrolyze triacetylglycerol (triacetin) and tributyrylglycerol (tributyrin), but not trioleylglycerol (triolein) or cholesterol oleate. Negatively regulates MalT activity by antagonizing maltotriose binding. Inhibits MelA galactosidase activity.[1] [2] [3] Publication Abstract from PubMedThe acyl esterase Aes effectively inhibits the transcriptional activity of MalT - the central activator of maltose and maltodextrin utilizing genes in Escherichia coli. To provide better insight into the nature of the interaction between Aes and MalT, we determined two different crystal structures of Aes - in its native form and covalently modified by a phenylmethylsulfonyl moiety at its active site serine. Both structures show distinct space groups and were refined to a resolution of 1.8 A and 2.3 A, respectively. The overall structure of Aes resembles a canonical alpha beta-hydrolase fold, which is extended by a funnel-like cap structure that forms the substrate-binding site. The catalytic triad of Aes, comprising residues Ser165, His292, and Asp262, is located at the bottom of this funnel. Analysis of the crystal-packing contacts of the two different space groups as well as analytical size exclusion chromatography revealed a homodimeric arrangement of Aes. The Aes dimer adopts an antiparallel contact involving both the hydrolase core and the cap, with its two-fold axis perpendicular to the largest dimension of Aes. In order to identify the surface area of Aes that is responsible for the interaction with MalT, we performed a structure-based alanine-scanning mutagenesis to identify Aes residues that are significantly impaired in MalT inhibition, but still exhibit wildtype expression and enzymatic activity. These residues map to a shallow slightly concave surface patch of Aes at the opposite site of the dimerization interface and indicate the surface area that interacts with MalT. (c) Proteins 2013. (c) 2013 Wiley Periodicals, Inc. Structural and mutational analyses of Aes, an inhibitor of MalT in Escherichia coli.,Schiefner A, Gerber K, Brosig A, Boos W Proteins. 2013 Aug 12. doi: 10.1002/prot.24383. PMID:23934774[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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