Characteristics of the bovicin HJ50 gene cluster in Streptococcus bovis HJ50

Abstract

Bovicin HJ50 is a new lantibiotic containing a disulfide bridge produced by Streptococcus bovis HJ50; its encoding gene bovA was reported in our previous publication. To identify other genes involved in bovicin HJ50 production, DNA fragments flanking bovA were cloned and sequenced. The bovicin HJ50 biosynthesis gene locus was encoded by a 9.9 kb region of chromosomal DNA and consisted of at least nine genes in the following order: bovA, -M, -T, -E, -F, ORF1, ORF2, bovK and bovR. A thiol-disulfide oxidoreductase gene named sdb1 was located downstream of bovR. A knockout mutant of this gene retained antimicrobial activity and the molecular mass of bovicin HJ50 in the mutant was the same as that of bovicin HJ50 in S. bovis HJ50, implying that sdb1 is not involved in bovicin HJ50 production. Transcriptional analyses showed that bovA, bovM and bovT constituted an operon, and the transcription start site of the bovA promoter was located at a G residue 45 bp upstream of the translation start codon for bovA, while bovE through bovR were transcribed together and the transcription start site of the bovE promoter was located at a C residue 35 bp upstream of bovE. We also demonstrated successful heterologous expression of bovicin HJ50 in Lactococcus lactis MG1363, which lacks thiol-disulfide oxidoreductase genes; this showed that thiol-disulfide oxidoreductase genes other than sdb1 are not essential for bovicin HJ50 biosynthesis.

Autoregulation of Lantibiotic Bovicin HJ50 Biosynthesis by the BovK-BovR Two-Component Signal Transduction System in Streptococcus bovis HJ50

“…The gene products of bovK and bovR in the bovicin HJ50 biosynthesis gene locus show significant sequence similarity to SalK and SalR, respectively, which are thought to compose a two-component system to regulate salivaricin A production (40). Therefore, BovK-BovR was predicted to be a two-component system to regulate the production of bovicin HJ50 (22). However, little is known about the transcriptional regulation of bovicin HJ50 biosynthesis, and the inducing signal and whether it is sensed by the BovK-BovR two-component system remain unknown.…”

Restoration of Bioactive Lantibiotic Suicin from a Remnant lan Locus of Pathogenic Streptococcus suis Serotype 2

“…As expected, SuiM 1 could not produce any dehydrated SuiA, supporting the idea that disruption of lanM might abolish lantibiotic production (32,43), whereas reconstituted intact SuiM produced SuiA with two dehydrations, indicating that its modification function had been restored. SuiT 159 , the peptidase domain of transporter SuiT, performed a digestion function at the double-Gly site to release mature suicin, which was confirmed by antimicrobial assay and MS analysis.…”

“…1B), suggesting its primary function of suicin biosynthesis. The bovicin HJ50 gene cluster was resequenced and reannotated here on the basis of the finding that bovT was actually one gene instead of two separate genes (bovT and bovE) as first annotated (32). In addition, orf1 and orf2 were reannotated as bovE and bovG, and bovI, located downstream of bovR, was unveiled.…”

Functional Analysis of Paralogous Thiol-disulfide Oxidoreductases in Streptococcus gordonii

“…Among the few TDORs that have been identified in Grampositive species, there are several examples of systems dedicated to bacteriocin production, including B. subtilis 168 BdbAB, S. thermophilus LMD BlpG (ST) , and Streptococcus bovis HJ50 Sdb1 (37,56,57). Despite the annotation as a bacteriocin transport accessory protein, Sgo.1216 did not affect bacteriocin production, and the function of this protein remains unknown.…”