title: The Mycobacterium tuberculosis LipB enzyme functions as a cysteine/lysine dyad acyltransferase.
abstract: Lipoic acid is essential for the activation of a number of protein complexes involved in key metabolic processes. Growth of Mycobacterium tuberculosis relies on a pathway in which the lipoate attachment group is synthesized from an endogenously produced octanoic acid moiety. In patients with multiple-drug-resistant M. tuberculosis, expression of one gene from this pathway, lipB, encoding for octanoyl-[acyl carrier protein]-protein acyltransferase is considerably up-regulated, thus making it a potential target in the search for novel antiinfectives against tuberculosis. Here we present the crystal structure of the M. tuberculosis LipB protein at atomic resolution, showing an unexpected thioether-linked active-site complex with decanoic acid. We provide evidence that the transferase functions as a cysteine/lysine dyad acyltransferase, in which two invariant residues (Lys-142 and Cys-176) are likely to function as acid/base catalysts. Analysis by MS reveals that the LipB catalytic reaction proceeds by means of an internal thioesteracyl intermediate. Structural comparison of LipB with lipoate protein ligase A indicates that, despite conserved structural and sequence active-site features in the two enzymes, 4'-phosphopantetheine-bound octanoic acid recognition is a specific property of LipB.
authors.affiliation: EMBL-Hamburg Unit, European Molecular Biology Laboratory, Notkestrasse 85, 22603 Hamburg, Germany.
authors.forename: Qingjun
authors.initials: Q
authors.lastname: Ma
authors.forename: Xin
authors.initials: X
authors.lastname: Zhao
authors.forename: Ali
authors.initials: A
authors.lastname: Nasser Eddine
authors.forename: Arie
authors.initials: A
authors.lastname: Geerlof
authors.forename: Xinping
authors.initials: X
authors.lastname: Li
authors.forename: John E
authors.initials: JE
authors.lastname: Cronan
authors.forename: Stefan H E
authors.initials: SH
authors.lastname: Kaufmann
authors.forename: Matthias
authors.initials: M
authors.lastname: Wilmanns
mesh_terms: D000217:Acyltransferases / Q000737:chemistry / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism*; D003652:Decanoic Acids / Q000737:chemistry; D008239:Lysine / Q000378:metabolism*; D013058:Mass Spectrometry; D008958:Models, Molecular; D009169:Mycobacterium tuberculosis / Q000201:enzymology*
chemical_list: D003652:Decanoic Acids; D000217:Acyltransferases; D008239:Lysine; D003545:Cysteine