title: Structure and biosynthesis of the BT peptide antibiotic from Brevibacillus texasporus.
abstract: We isolated a novel gram-positive bacterium, Brevibacillus texasporus, that produces an antibiotic, BT. BT is a group of related peptides that are produced by B. texasporus cells in response to nutrient limitation. We report here purification and determination of the structure of the most abundant BT isomer, BT1583. Amino acid composition and tandem mass spectrometry experiments yielded a partial BT1583 structure. The presence of ornithine and d-form residues in the partial BT1583 structure indicated that the peptide is synthesized by a nonribosomal peptide synthetase (NRPS). The BT NRPS operon was rapidly and accurately identified by using a novel in silico NRPS operon hunting strategy that involved direct shotgun genomic sequencing rather than the unreliable cosmid library hybridization scheme. Sequence analysis of the BT NRPS operon indicated that it encodes a colinear modular NRPS with a strict correlation between the NRPS modules and the amino acid residues in the peptide. The colinear nature of the BT NRPS enabled us to utilize the genomic information to refine the BT1583 peptide sequence to Me(2)-4-methyl-4-[(E)-2-butenyl]-4,N-methyl-threonine-L-dO-I-V-V-dK-V-dL-K-dY-L-V-CH2OH. In addition, we report the discovery of novel NRPS codons (sets of the substrate specificity-conferring residues in NRPS modules) for valine, lysine, ornithine, and tyrosine.
authors.affiliation: Department of Medical Biochemistry and Genetics, 428 Reynolds Medical Building, Texas A&M University System Health Science Center, College Station, TX 77843-1114, USA.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Wu
authors.forename: Johnathan
authors.initials: J
authors.lastname: Ballard
authors.forename: Yi Wei
authors.initials: YW
authors.lastname: Jiang
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000096:biosynthesis* / Q000737:chemistry / Q000494:pharmacology; D001407:Bacillus / Q000235:genetics / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D016384:Consensus Sequence; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D016680:Genome, Bacterial; D015698:Genomic Library; D007536:Isomerism; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000096:biosynthesis / Q000737:chemistry* / Q000494:pharmacology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D000900:Anti-Bacterial Agents; C507515:BT peptide antibiotic, Brevibacillus texasporus; D004269:DNA, Bacterial; D009842:Oligopeptides