title: The essential mycobacterial genes, fabG1 and fabG4, encode 3-oxoacyl-thioester reductases that are functional in yeast mitochondrial fatty acid synthase type 2.
abstract: Mycobacterium tuberculosis represents a severe threat to human health worldwide. Therefore, it is important to expand our knowledge of vital mycobacterial processes, such as that effected by fatty acid synthase type 2 (FASII), as well as to uncover novel ones. Mycobacterial FASII undertakes mycolic acid biosynthesis, which relies on a set of essential enzymes, including 3-oxoacyl-AcpM reductase FabG1/Rv1483. However, the M. tuberculosis genome encodes four additional FabG homologs, designated FabG2-FabG5, whose functions have hitherto not been characterized in detail. Of the four candidates, FabG4/Rv0242c was recently shown to be essential for the survival of M. bovis BCG. The present work was initiated by assessing the suitability of yeast oar1Delta mutant cells lacking mitochondrial 3-oxoacyl-ACP reductase activity to act as a surrogate system for expressing FabG1/MabA directed to the mitochondria. Mutant yeast cells producing this targeted FabG1 variant were essentially wild type for all of the chronicled phenotype characteristics, including respiratory growth on glycerol medium, cytochrome assembly and lipoid acid production. This indicated that within the framework of de novo fatty acid biosynthesis in yeast mitochondria, FabG1 was able to act on shorter (C(4)) acyl substrates than was previously proposed (C(8-20)) during mycolic acid biosynthesis in M. tuberculosis. Thereafter, FabG2-FabG5 were expressed as mitochondrial proteins in the oar1Delta strain, and FabG4 was found to complement the mutant phenotype and contain high levels of 3-oxoacyl-thioester reductase activity. Hence, like FabG1, FabG4 is also an essential, physiologically functional 3-oxoacyl-thioester reductase, albeit the latter's involvement in mycobacterial FASII remains to be explored.
authors.affiliation: Section of Physiology of Lipid Metabolism, Institute of Physiology, Center for Physiology, Pathophysiology and Immunology, Medical University of Vienna, Schwarzspanierstrasse 17, Vienna 1090, Austria. aner.gurvitz@meduniwien.ac.at
authors.forename: Aner
authors.initials: A
authors.lastname: Gurvitz
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics* / Q000502:physiology*; D000595:Amino Acid Sequence; D019069:Cell Respiration / Q000235:genetics; D054889:Fatty Acid Synthase, Type II / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal / Q000502:physiology; D005816:Genetic Complementation Test; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D030781:Organisms, Genetically Modified; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D008063:Thioctic Acid / Q000378:metabolism
chemical_list: D008063:Thioctic Acid; D000429:Alcohol Oxidoreductases; C023744:acetoacetyl-CoA reductase; D054889:Fatty Acid Synthase, Type II
references.citation: Mol Microbiol. 2003 Apr;48(1):77-84
references.pmid: 12657046
references.citation: Science. 1994 Jan 14;263(5144):227-30
references.pmid: 8284673
references.citation: Proc Natl Acad Sci U S A. 2003 Oct 28;100(22):12989-94
references.pmid: 14569030
references.citation: Yeast. 1986 Sep;2(3):163-7
references.pmid: 3333305
references.citation: Mol Cell Biol. 2001 Sep;21(18):6243-53
references.pmid: 11509667
references.citation: J Biol Chem. 1997 Aug 29;272(35):22140-7
references.pmid: 9268358
references.citation: J Bacteriol. 2008 Jun;190(11):4088-90
references.pmid: 18375556
references.citation: J Biomed Biotechnol. 2009;2009:235868
references.pmid: 19746209
references.citation: EMBO J. 1996 Jun 17;15(12):2924-34
references.pmid: 8670793
references.citation: FASEB J. 2009 Nov;23(11):3682-91
references.pmid: 19571038
references.citation: Antimicrob Agents Chemother. 2004 Jan;48(1):242-9
references.pmid: 14693546
references.citation: Adv Enzymol Relat Areas Mol Biol. 1977;45:1-84
references.pmid: 21523
references.citation: Acta Crystallogr D Biol Crystallogr. 2002 Feb;58(Pt 2):303-5
references.pmid: 11807257
references.citation: Biochemistry. 1996 Jul 30;35(30):9797-806
references.pmid: 8703953
references.citation: Antimicrob Agents Chemother. 2002 Nov;46(11):3362-9
references.pmid: 12384337
references.citation: FEBS Lett. 1997 May 19;408(2):217-20
references.pmid: 9187370
references.citation: J Bacteriol. 2007 May;189(10):3721-8
references.pmid: 17337570
references.citation: Anal Biochem. 1976 May 7;72:248-54
references.pmid: 942051
references.citation: Curr Genet. 1997 Dec;32(6):384-8
references.pmid: 9388293
references.citation: Biochem Soc Trans. 2005 Nov;33(Pt 5):1162-5
references.pmid: 16246072
references.citation: J Bacteriol. 2009 Apr;191(8):2683-90
references.pmid: 19136596
references.citation: Clin Microbiol Rev. 2005 Jan;18(1):81-101
references.pmid: 15653820
references.citation: Arch Biochem Biophys. 1958 Nov;78(1):66-82
references.pmid: 13595904
references.citation: Nature. 1998 Jun 11;393(6685):537-44
references.pmid: 9634230
references.citation: Mol Microbiol. 2004 Dec;54(5):1161-72
references.pmid: 15554959
references.citation: Microbiology (Reading). 2002 Apr;148(Pt 4):951-960
references.pmid: 11932442
references.citation: Microbiology (Reading). 2002 Oct;148(Pt 10):2975-2986
references.pmid: 12368431
references.citation: PLoS One. 2009 Apr 28;4(4):e5349
references.pmid: 19479006
references.citation: Antimicrob Agents Chemother. 2003 Sep;47(9):2903-13
references.pmid: 12936993
references.citation: J Mol Biol. 2005 Nov 4;353(4):847-58
references.pmid: 16213523
references.citation: J Biol Chem. 1995 Nov 17;270(46):27453-7
references.pmid: 7499202
references.citation: Microbiology (Reading). 1998 Oct;144 ( Pt 10):2697-2704
references.pmid: 9802011
references.citation: Biochemistry. 2006 Nov 28;45(47):13947-53
references.pmid: 17115689
references.citation: Appl Environ Microbiol. 2008 Aug;74(16):5078-85
references.pmid: 18552191
references.citation: Curr Genet. 1992 Jan;21(1):83-4
references.pmid: 1735128
references.citation: J Biol Chem. 1961 Oct;236:2620-3
references.pmid: 13899833
references.citation: Gene. 1993 Sep 30;132(1):49-55
references.pmid: 8406042
references.citation: J Biol Chem. 1984 Feb 10;259(3):1781-8
references.pmid: 6363415
references.citation: Biochemistry. 1993 Apr 13;32(14):3778-82
references.pmid: 8466915