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The putative fabJ gene of Escherichia coli fatty acid synthesis is the fabF gene.

ABSTRACT: Siggaard-Andersen and coworkers (M. Siggaard-Andersen, M. Wissenbach, J. Chuck, I. Svendsen, J. G. Olsen, and P. von Wettstein-Knowles, Proc. Natl. Acad. Sci. USA 91:11027-11031, 1994) recently reported the DNA sequence of a gene encoding a beta-ketoacyl-acyl carrier protein synthase from Escherichia coli. These workers assigned this gene the designation fabJ and reported that the gene encoded a new beta-ketoacyl-acyl carrier protein synthase. We report that the fabJ gene is the previously reported fabF gene that encodes the known beta-ketoacyl-acyl carrier protein synthase II.

SUBMITTER: Magnuson K

PROVIDER: S-EPMC177068 | biostudies-other | 1995 Jun

REPOSITORIES: biostudies-other

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The putative fabJ gene of Escherichia coli fatty acid synthesis is the fabF gene.

Magnuson K K Carey M R MR Cronan J E JE

Journal of bacteriology 19950601 12

Siggaard-Andersen and coworkers (M. Siggaard-Andersen, M. Wissenbach, J. Chuck, I. Svendsen, J. G. Olsen, and P. von Wettstein-Knowles, Proc. Natl. Acad. Sci. USA 91:11027-11031, 1994) recently reported the DNA sequence of a gene encoding a beta-ketoacyl-acyl carrier protein synthase from Escherichia coli. These workers assigned this gene the designation fabJ and reported that the gene encoded a new beta-ketoacyl-acyl carrier protein synthase. We report that the fabJ gene is the previously repor ...[more]

PMID: 7768872

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Project description:Type II fatty acid biosynthesis in bacteria can be broadly classified into the initiation and elongation phases. The biochemical functions defining each step in the two phases have been studied in vitro Among the ?-ketoacyl-acyl carrier protein (ACP) synthases, FabH catalyzes the initiation reaction, while FabB and FabF, which primarily catalyze the elongation reaction, can also drive initiation as side reactions. A role for FabB and FabF in the initiation of fatty acid biosynthesis would be supported by the viability of the ?fabH mutant. In this study, we show that the ?fabH and ?yiiD mutations were synthetically lethal and that ?fabH ?relA ?spoT and ?fabH ?dksA synthetic lethality was rescued by the heterologous expression of yiiD In the ?fabH mutant, the expression of yiiD was positively regulated by (p)ppGpp. The growth defect, reduced cell size, and altered fatty acid profile of the ?fabH mutant and the growth defect of the ?fabH ?fabF fabB15(Ts) mutant in oleate- and palmitate-supplemented medium at 42°C were rescued by the expression of yiiD from a multicopy plasmid. Together, these results indicate that the yiiD-encoded function supported initiation of fatty acid biosynthesis in the absence of FabH. We have renamed yiiD as fabY IMPORTANCE Fatty acid biosynthesis is an essential process conserved across life forms. ?-Ketoacyl-ACP synthases are essential for fatty acid biosynthesis. FabH is a ?-ketoacyl-ACP synthase that contributes to the initiation of fatty acid biosynthesis in Escherichia coli In this study, we present genetic and biochemical evidence that the yiiD (renamed fabY)-encoded function contributes to the biosynthesis of fatty acid in the absence of FabH activity and that under these conditions, the expression of FabY was regulated by the stringent response factors (p)ppGpp and DksA. Combined inactivation of FabH and FabY resulted in growth arrest, possibly due to the loss of fatty acid biosynthesis. A molecule(s) that inhibits the two activities can be an effective microbicide.

Project description:UNLABELLED: BACKGROUND:Thioesterases remove the fatty acyl moiety from the fatty acyl-acyl carrier proteins (ACPs), releasing them as free fatty acids (FFAs), which can be further used to produce a variety of fatty acid-based biofuels, such as biodiesel, fatty alcohols and alkanes. Thioesterases play a key role in the regulation of the fatty acid synthesis in Escherichia coli. Therefore, exploring more promising thioesterases will contribute to the development of industrial microbial lipids production. RESULTS:We cloned and expressed a cytosolic Acinetobacter baylyi thioesterase ('AcTesA) in E. coli by deleting its leader sequence. Protein sequence alignment, structure modeling and site-directed mutagenesis demonstrated that Ser10, Gly48, Asn77, Asp158 and His161 residues composed the active centre of 'AcTesA. The engineered strain that overexpressed 'AcTesA achieved a FFAs titer of up to 501.2 mg/L in shake flask, in contrast to only 20.5 mg/L obtained in wild-type E. coli, demonstrating that the expression of 'AcTesA indeed boosted the synthesis of FFAs. The 'AcTesA exhibited a substrate preference towards the C8-C16 acyl groups, with C14:0, C16:1, C12:0 and C8:0 FFAs being the top four components. Optimization of expression level of 'AcTesA made the FFAs production increase to 551.3 mg/L. The FFAs production further increased to 716.1 mg/L by optimization of the culture medium. Fed-batch fermentation was also carried out to evaluate the FFAs production in a scaleable process. Finally, 3.6 g/L FFAs were accumulated within 48 h, and a maximal FFAs yield of 6.1% was achieved in 12-16 h post induction. CONCLUSIONS:For the first time, an A. baylyi thioesterase was cloned and solubly expressed in the cytosol of E. coli. This leaderless thioesterase ('AcTesA) was found to be capable of enhancing the FFAs production of E. coli. Without detailed optimization of the strain and fermentation, the finally achieved 3.6 g/L FFAs is encouraging. In addition, 'AcTesA exhibited different substrate specificity from other thioesterases previously reported, and can be used to supply the fatty acid-based biofuels with high quality of FFAs. Altogether, this study provides a promising thioesterase for FFAs production, and is of great importance in enriching the library of useful thioesterases.

Dataset Information

The putative fabJ gene of Escherichia coli fatty acid synthesis is the fabF gene.

Publications

The putative fabJ gene of Escherichia coli fatty acid synthesis is the fabF gene.

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