Structural and functional organization of the fengycin synthetase multienzyme system from Bacillus subtilis b213 and A1/3

Abstract

Background: Bacillus subtilis strains produce a broad spectrum of lipopeptides that are potent biosurfactants and have specific antimicrobial and antiviral activities. The cyclic lipodecapeptide fengycin is one such compound. Although the fengycin biosynthetic genes in B. subtilis 168 (pps genes) and F29-3 (fen genes) have been well characterized, only limited information is available about the biochemical features of the fengycin synthetase multienzyme system.

Results: Five multifunctional peptide synthetases (Fen1-5) that catalyze biosynthesis of the peptide portion of fengycin have been purified from crude extracts of the B. subtilis b213 and A1/3 strains. These enzymes activate all fengycin amino-acid components as aminoacyl adenylates or aminoacyl thioesters. Fen1, Fen2 and Fen3 are each approximately 286 kDa, Fen4 is approximately 400 kDa and Fen 5 is approximately 140kDa; each enzyme activates a different set of L-amino acids. A five-gene cluster (fen1-5) was detected in the B. subtilis A1/3 genome that shows high homology to the pps and fen genes in B. subtilis strains 168 and F29-3. Disruption of fen4 resulted in a loss of fengycin production. The fengycin synthetase enzymes isolated from B. subtilis b213 were assigned to the corresponding A1/3 fen genes by their amino-terminal sequences.

Conclusions: The structural and functional organization of the fengycin synthetase system from B. subtilis b213 has been characterized in detail and correlated with the corresponding pps and fen genes in B. subtilis strains 168, A1/3 and F29-3. Biosynthesis of the peptide part of fengycin involves five multifunctional modular proteins that assemble the lipopeptide chain using a nonribosomal, multiple carrier thiotemplate mechanism.