title: Characterization of the biotin uptake system encoded by the biotin-inducible bioYMN operon of Corynebacterium glutamicum.
abstract: BACKGROUND
  The amino acid-producing Gram-positive Corynebacterium glutamicum is auxotrophic for biotin although biotin ring assembly starting from the precursor pimeloyl-CoA is still functional. It possesses AccBC, the α-subunit of the acyl-carboxylases involved in fatty acid and mycolic acid synthesis, and pyruvate carboxylase as the only biotin-containing proteins. Comparative genome analyses suggested that the putative transport system BioYMN encoded by cg2147, cg2148 and cg2149 might be involved in biotin uptake by C. glutamicum.
  
  
  RESULTS
  By comparison of global gene expression patterns of cells grown with limiting or excess supply of biotin or with dethiobiotin as supplement replacing biotin revealed that expression of genes coding for enzymes of biotin ring assembly and for the putative uptake system was regulated according to biotin availability. RT-PCR and 5'-RACE experiments demonstrated that the genes bioY, bioM, and bioN are transcribed from one promoter as a single transcript. Biochemical analyses revealed that BioYMN catalyzes the effective uptake of biotin with a concentration of 60 nM biotin supporting a half-maximal transport rate. Maximal biotin uptake rates were at least five fold higher in biotin-limited cells as compared to cells grown with excess biotin. Overexpression of bioYMN led to an at least 50 fold higher biotin uptake rate as compared to the empty vector control. Overproduction of BioYMN alleviated biotin limitation and interfered with triggering L-glutamate production by biotin limitation.
  
  
  CONCLUSIONS
  The operon bioYMN from C. glutamicum was shown to be induced by biotin limitation. Transport assays with radio-labeled biotin revealed that BioYMN functions as a biotin uptake system. Overexpression of bioYMN affected L-glutamate production triggered by biotin limitation.
authors.affiliation: Genetics of Prokaryotes, Faculty of Biology and CeBiTec, Bielefeld University, Bielefeld, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Schneider
authors.forename: Petra
authors.initials: P
authors.lastname: Peters-Wendisch
authors.forename: K Corinna
authors.initials: KC
authors.lastname: Stansen
authors.forename: Susanne
authors.initials: S
authors.lastname: Götker
authors.forename: Stanislav
authors.initials: S
authors.lastname: Maximow
authors.forename: Reinhard
authors.initials: R
authors.lastname: Krämer
authors.forename: Volker F
authors.initials: VF
authors.lastname: Wendisch
mesh_terms: D001692:Biological Transport; D001710:Biotin / Q000378:metabolism*; D048230:Corynebacterium glutamicum / Q000235:genetics* / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D009876:Operon; D024363:Transcription Initiation Site; D014158:Transcription, Genetic
chemical_list: D026901:Membrane Transport Proteins; D001710:Biotin