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Chem Biol. 1997 Dec;4(12):927-37.

The bacitracin biosynthesis operon of Bacillus licheniformis ATCC 10716: molecular characterization of three multi-modular peptide synthetases.

Author information

1
Philipps-Universität Marburg Fachbereich Chemie/Biochemie Hans-Meerwein-Strasse, 35032, Marburg, Germany.

Abstract

BACKGROUND:

The branched cyclic dodecylpeptide antibiotic bacitracin, produced by special strains of Bacillus, is synthesized nonribosomally by a large multienzyme complex composed of the three bacitracin synthetases BA1, BA2 and BA3. These enzymes activate and incorporate the constituent amino acids of bacitracin by a thiotemplate mechanism in a pathway driven by a protein template. The biochemical features of these enzymes have been studied intensively but little is known about the molecular organization of their genes.

RESULTS:

The entire bacitracin synthetase operon containing the genes bacA-bacC was cloned and sequenced, identifying a modular structure typical of peptide synthetases. The bacA gene product (BA1, 598kDa) contains five modules, with an internal epimerization domain attached to the fourth; bacB encodes BA2 (297kDa), and has two modules and a carboxy-terminal epimerization domain; bacC encodes BA3, five modules (723kDa) with additional internal epimerization domains attached to the second and fourth. A carboxy-terminal putative thioesterase domain was also detected in BA3. A putative cyclization domain was found in BA1 that may be involved in thiazoline ring formation. The adenylation/thioester-binding domains of the first two BA1 modules were overproduced and the detected amino-acid specificity coincides with the first two amino acids in bacitracin. Disruption of chromosomal bacB resulted in a bacitracin-deficient mutant.

CONCLUSIONS:

The genes encoding the bacitracin synthetases BA1, BA2 and BA3 are organized in an operon, the structure of which reflects the modular architecture expected of peptide synthetases. In addition, a putative thiazoline ring formation domain was identified in the BA1 gene.

PMID:
9427658
DOI:
10.1016/s1074-5521(97)90301-x
[Indexed for MEDLINE]
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