1u6e | pdb_00001u6e
1.85 Angstrom Crystal Structure of the C112A Mutant of Mycobacterium Tuberculosis Beta-Ketoacyl-Acyl Carrier Protein Synthase III (FabH)
Structural highlights
FunctionFABH_MYCTU Catalyzes the condensation reaction of fatty acid synthesis by the addition to an acyl acceptor of two carbons from malonyl-ACP. Catalyzes the first condensation reaction which initiates fatty acid synthesis and may therefore play a role in governing the total rate of fatty acid production. Possesses both acetoacetyl-ACP synthase and acetyl transacylase activities. Has some substrate specificity for long chain acyl-CoA such as myristoyl-CoA. Does not use acyl-CoA as primer. Its substrate specificity determines the biosynthesis of mycolic acid fatty acid chain, which is characteristic of mycobacterial cell wall.[1] 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 PubMedBeta-ketoacyl-acyl carrier protein synthase III (FabH) catalyzes a two step reaction that initiates the pathway of fatty acid biosynthesis in plants and bacteria. In Mycobacterium tuberculosis, FabH catalyzes extension of lauroyl, myristoyl and palmitoyl groups from which cell wall mycolic acids of the bacterium are formed. The first step of the reaction is an acyl group transfer from acyl-coenzyme A to the active-site cysteine of the enzyme; the second step is acyl chain extension by two carbon atoms through Claisen condensation with malonyl-acyl carrier protein. We have previously determined the crystal structure of a type II, dissociated M.tuberculosis FabH, which catalyzes extension of lauroyl, myristoyl and palmitoyl groups. Here we describe the first long-chain Michaelis substrate complex of a FabH, that of lauroyl-coenzyme A with a catalytically disabled Cys-->Ala mutant of M.tuberculosis FabH. An elongated channel extending from the mutated active-site cysteine defines the acyl group binding locus that confers unique acyl substrate specificity on M.tuberculosis FabH. CoA lies in a second channel, bound primarily through interactions of its nucleotide group at the enzyme surface. The apparent weak association of CoA in this complex may play a role in the binding and dissociation of long chain acyl-CoA substrates and products and poses questions pertinent to the mechanism of this enzyme. Crystal structure of a substrate complex of Mycobacterium tuberculosis beta-ketoacyl-acyl carrier protein synthase III (FabH) with lauroyl-coenzyme A.,Musayev F, Sachdeva S, Scarsdale JN, Reynolds KA, Wright HT J Mol Biol. 2005 Mar 11;346(5):1313-21. Epub 2005 Jan 20. PMID:15713483[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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