title: Divergence of function in the hot dog fold enzyme superfamily: the bacterial thioesterase YciA.
abstract: Thioesters play a central role in the cells where they participate in metabolism, membrane synthesis, signal transduction, and gene regulation. Thioesters are converted to the thiol and carboxylic acid components by thioesterase-catalyzed hydrolysis. Here we examine the biochemical and biological function of the hot dog fold thioesterase YciA (EcYciA) from Escherichia coli and its close sequence homologue HI0827 from Haemophilus influenzae (HiYciA). The quaternary structure of HiYciA was determined, using equilibrium sedimentation techniques, to be a homohexamer. Mass spectral and (31)P NMR analysis of purified HiYciA revealed a bound CoA ligand. Kinetic analyses showed that CoA is a strong feedback inhibitor. YciA thioesterase activity toward acyl-CoA substrates was determined using steady-state kinetic methods. The k cat and k cat/ K m values obtained reveal a striking combination of high catalytic efficiency and low substrate specificity. The substrate activity of propionyl-s- N-acetylcysteine was found to be negligible and that of n-butyryl-pantetheinephosphate low, and therefore, it is evident YciA does not target acylated ACPs or other acylated proteins as substrates. The results from bioinformatic analysis of the biological distribution and genome contexts of yciAs are reported. We conclude that YciA is responsible for the efficient, "seemingly" indiscriminant, CoA-regulated hydrolysis of cellular acyl-CoA thioesters in a wide range of bacteria and hypothesize that this activity may support membrane biogenesis.
authors.affiliation: Department of Chemistry, University of New Mexico, Albuquerque, New Mexico 81713, USA.
authors.forename: Zhihao
authors.initials: Z
authors.lastname: Zhuang
authors.forename: Feng
authors.initials: F
authors.lastname: Song
authors.forename: Hong
authors.initials: H
authors.lastname: Zhao
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.forename: Jian
authors.initials: J
authors.lastname: Cao
authors.forename: Edward
authors.initials: E
authors.lastname: Eisenstein
authors.forename: Osnat
authors.initials: O
authors.lastname: Herzberg
authors.forename: Debra
authors.initials: D
authors.lastname: Dunaway-Mariano
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D002384:Catalysis; D003065:Coenzyme A / Q000737:chemistry / Q000378:metabolism; D004789:Enzyme Activation; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D006193:Haemophilus influenzae / Q000378:metabolism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D021241:Spectrometry, Mass, Electrospray Ionization; D013379:Substrate Specificity; D013869:Thiolester Hydrolases / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D013869:Thiolester Hydrolases; D003065:Coenzyme A