title: The BioC O-methyltransferase catalyzes methyl esterification of malonyl-acyl carrier protein, an essential step in biotin synthesis.
abstract: Recent work implicated the Escherichia coli BioC protein as the initiator of the synthetic pathway that forms the pimeloyl moiety of biotin (Lin, S., Hanson, R. E., and Cronan, J. E. (2010) Nat. Chem. Biol. 6, 682-688). BioC was believed to be an O-methyltransferase that methylated the free carboxyl of either malonyl-CoA or malonyl-acyl carrier protein based on the ability of O-methylated (but not unmethylated) precursors to bypass the BioC requirement for biotin synthesis both in vivo and in vitro. However, only indirect proof of the hypothesized enzymatic activity was obtained because the activities of the available BioC preparations were too low for direct enzymatic assay. Because E. coli BioC protein was extremely recalcitrant to purification in an active form, BioC homologues of other bacteria were tested. We report that the native form of Bacillus cereus ATCC10987 BioC functionally replaced E. coli BioC in vivo, and the protein could be expressed in soluble form and purified to homogeneity. In disagreement with prior scenarios that favored malonyl-CoA as the methyl acceptor, malonyl-acyl carrier protein was a far better acceptor of methyl groups from S-adenosyl-L-methionine than was malonyl-CoA. BioC was specific for the malonyl moiety and was inhibited by S-adenosyl-L-homocysteine and sinefungin. High level expression of B. cereus BioC in E. coli blocked cell growth and fatty acid synthesis.
authors.affiliation: Department of Microbiology, University of Illinois, Urbana, Illinois 61801, USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Lin
authors.forename: John E
authors.initials: JE
authors.lastname: Cronan
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000737:chemistry; D000595:Amino Acid Sequence; D001409:Bacillus cereus / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001710:Biotin / Q000096:biosynthesis*; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D002850:Chromatography, Gel; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics; D005227:Fatty Acids / Q000096:biosynthesis; D005816:Genetic Complementation Test; D006863:Hydrogen-Ion Concentration; D008715:Methionine / Q000737:chemistry; D008969:Molecular Sequence Data; D011497:Protein O-Methyltransferase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012435:S-Adenosylhomocysteine / Q000737:chemistry; D012436:S-Adenosylmethionine / Q000096:biosynthesis; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D005227:Fatty Acids; D001710:Biotin; D012436:S-Adenosylmethionine; D000255:Adenosine Triphosphate; D012435:S-Adenosylhomocysteine; D008715:Methionine; D011497:Protein O-Methyltransferase; D000241:Adenosine; C006235:sinefungin