title: Profligate biotin synthesis in α-proteobacteria - a developing or degenerating regulatory system?
abstract: Biotin (vitamin H) is a key enzyme cofactor required in all three domains of life. Although this cofactor was discovered over 70 years ago and has long been recognized as an essential nutrient for animals, our knowledge of the strategies bacteria use to sense biotin demand is very limited. The paradigm mechanism is that of Escherichia coli in which BirA protein, the prototypical bi-functional biotin protein ligase, both covalently attaches biotin to the acceptor proteins of central metabolism and represses transcription of the biotin biosynthetic pathway in response to biotin demand. However, in other bacteria the biotin protein ligase lacks a DNA-binding domain which raises the question of how these bacteria regulate the synthesis of biotin, an energetically expensive molecule. A bioinformatic study by Rodionov and Gelfand identified a protein termed BioR in α-proteobacteria and predicted that BioR would have the biotin operon regulatory role that in most other bacteria is fulfilled by the BirA DNA-binding domain. We have now tested this prediction in the plant pathogen Agrobacterium tumefaciens. As predicted the A. tumefaciens biotin protein ligase is a fully functional ligase that has no role in regulation of biotin synthesis whereas BioR represses transcription of the biotin synthesis genes. Moreover, as determined by electrophoretic mobility shift assays, BioR binds the predicted operator site, which is located downstream of the mapped transcription start site. qPCR measurements indicated that deletion of BioR resulted in a c. 15-fold increase of bio operon transcription in the presence of high biotin levels. Effective repression of a plasmid-borne bioB-lacZ reporter was seen only upon the overproduction of BioR. In contrast to E. coli and Bacillus subtilis where biotin synthesis is tightly controlled, A. tumefaciens synthesizes much more biotin than needed for modification of the biotin-requiring enzymes. Protein-bound biotin constitutes only about 0.5% of the total biotin, most of which is found in the culture medium. To the best of our knowledge, A. tumefaciens represents the first example of profligate biotin synthesis by a wild type bacterium.
authors: Department of Microbiology, University of Illinois, Urbana, IL 61801, USA.
authors: Youjun
authors: Y
authors: Feng
authors: Huimin
authors: H
authors: Zhang
authors: John E
authors: JE
authors: Cronan
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001710:Biotin / Q000096:biosynthesis*; D019921:Biotinylation; D019731:Carbon-Nitrogen Ligases / Q000737:chemistry / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D005798:Genes, Bacterial / Q000235:genetics; D008024:Ligands; D026901:Membrane Transport Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D009876:Operon / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D012097:Repressor Proteins / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D008024:Ligands; D026901:Membrane Transport Proteins; D012097:Repressor Proteins; D001710:Biotin; D019731:Carbon-Nitrogen Ligases
references: Nat Chem Biol. 2010 Sep;6(9):682-8
references: 20693992
references: Mol Microbiol. 2011 Apr;80(1):195-218
references: 21276098
references: Methods Mol Biol. 1995;44:1-7
references: 7581656
references: J Bacteriol. 1980 Aug;143(2):789-800
references: 6782078
references: Proc Natl Acad Sci U S A. 1992 Oct 1;89(19):9257-61
references: 1409631
references: J Bacteriol. 2012 Mar;194(5):1113-26
references: 22210766
references: J Biol Chem. 2001 Oct 5;276(40):37355-64
references: 11495922
references: Methods. 2001 Dec;25(4):402-8
references: 11846609
references: J Bacteriol. 1996 Jul;178(14):4122-30
references: 8763940
references: Cell. 1989 Aug 11;58(3):427-9
references: 2667763
references: Mol Plant Microbe Interact. 1992 May-Jun;5(3):228-34
references: 1421510
references: EMBO J. 2002 Aug 15;21(16):4349-56
references: 12169637
references: Annu Rev Genet. 2007;41:443-64
references: 17669049
references: PLoS One. 2012;7(9):e46275
references: 23029459
references: FEMS Microbiol Lett. 2006 Feb;255(1):102-7
references: 16436068
references: J Mol Biol. 2011 Aug 26;411(4):729-43
references: 21699902
references: Biochemistry. 2002 Dec 3;41(48):14263-71
references: 12450391
references: Genome Res. 2002 Oct;12(10):1507-16
references: 12368242
references: J Biol Chem. 2009 Oct 23;284(43):29526-35
references: 19679654
references: Nature. 1978 Dec 14;276(5689):689-94
references: 366433
references: Mol Plant Microbe Interact. 2001 Jan;14(1):98-103
references: 11194879
references: Plasmid. 1984 May;11(3):206-20
references: 6087391
references: Appl Environ Microbiol. 2001 Sep;67(9):3860-5
references: 11525978
references: J Bacteriol. 2001 Dec;183(24):7371-80
references: 11717296
references: Protein Sci. 2004 Nov;13(11):3043-50
references: 15459338
references: Science. 2001 Dec 14;294(5550):2317-23
references: 11743193
references: Proc Natl Acad Sci U S A. 2001 May 22;98(11):6045-50
references: 11353844
references: Proc Natl Acad Sci U S A. 2007 Feb 20;104(8):2909-14
references: 17301237
references: Methods Enzymol. 1991;204:384-97
references: 1658565
references: Proc Natl Acad Sci U S A. 2003 Sep 2;100(18):10181-6
references: 12928499
references: Biochemistry. 1994 Jun 14;33(23):7354-60
references: 8003500
references: Gene. 1990 Mar 1;87(1):63-70
references: 2110099
references: Biochemistry. 1998 Mar 3;37(9):3210-9
references: 9485476
references: Science. 2001 Dec 14;294(5550):2323-8
references: 11743194
references: J Bacteriol. 2010 Sep;192(17):4289-99
references: 20622065
references: J Biotechnol. 2012 Jun 15;159(3):225-34
references: 22178235
references: Biochem Biophys Res Commun. 1965 Jun 9;19(6):777-82
references: 5840700
references: Biochemistry. 1999 Oct 5;38(40):13077-84
references: 10529178
references: Nat Biotechnol. 2001 Aug;19(8):751-5
references: 11479568
references: J Bacteriol. 1995 May;177(9):2572-5
references: 7730294
references: Mol Microbiol. 2011 Aug;81(4):1020-33
references: 21771112
references: EMBO J. 1990 Apr;9(4):973-9
references: 2182324
references: Gene. 1991 Dec 1;108(1):39-45
references: 1761229
references: J Biol Chem. 1969 Mar 25;244(6):1393-8
references: 5775781
references: J Bacteriol. 2009 Oct;191(20):6320-8
references: 19684132
references: J Mol Biol. 1998 May 15;278(4):787-800
references: 9614942
references: Appl Environ Microbiol. 2008 Aug;74(16):5053-62
references: 18606801
references: J Bacteriol. 1995 Jul;177(14):4121-30
references: 7608087
references: Biochem J. 1994 Sep 15;302 ( Pt 3):881-7
references: 7945216