SrrB, a Pseudo-Receptor Protein, Acts as a Negative Regulator for Lankacidin and Lankamycin Production in Streptomyces rochei

Abstract

Streptomyces rochei 7434AN4, a producer of lankacidin (LC) and lankamycin (LM), carries many regulatory genes including a biosynthesis gene for signaling molecules SRBs (srrX), an SRB receptor gene (srrA), and a SARP (Streptomyces antibiotic regulatory protein) family activator gene (srrY). Our previous study revealed that the main regulatory cascade goes from srrX through srrA to srrY, leading to LC production, whereas srrY further regulates a second SARP gene srrZ to synthesize LM. In this study we extensively investigated the function of srrB, a pseudo-receptor gene, by analyzing antibiotic production and transcription. Metabolite analysis showed that the srrB mutation increased both LC and LM production over four-folds. Transcription, gel shift, and DNase I footprinting experiments revealed that srrB and srrY are expressed under the SRB/SrrA regulatory system, and at the later stage, SrrB represses srrY expression by binding to the promoter region of srrY. These findings confirmed that SrrB acts as a negative regulator of the activator gene srrY to control LC and LM production at the later stage of fermentation in S. rochei.

Functional Analysis of P450 Monooxygenase SrrO in the Biosynthesis of Butenolide-Type Signaling Molecules in Streptomyces rochei

“…Preparation of an SrrA protein (SRB receptor) and a DNA probe containing the promoter region of srrY ( srrYp ), a target gene of SrrA, was described previously [ 22 , 38 ]. The reaction mixture contained the binding buffer (20 mM Tris-HCl [pH 8.0], 100 mM NaCl, 1 mM dithiothreitol, 0.1 mg of bovine serum albumin and 5% glycerol), 0.35 nM labeled DNA, and 2 μM SrrA protein.…”

Rethinking Biosynthesis of Aclacinomycin A

“…The A-Factors bind to cytoplasmic receptors (e.g., TetR family regulators) and activate gene transcription [ 136 ]. Relying on this principle, the levels of secondary metabolites in Streptomyces could be enhanced by the exogenous addition of A-Factor analogues or the manipulation of signal-molecule-related genes [ 137 , 138 , 139 ]. Since SARP family proteins are pathway-specific regulators, the overexpression of SARP regulator DnrI and AfsR lead to improved production of DNR and DXR [ 140 , 141 ].…”

Isolation of Hydrazide-alkenes with Different Amino Acid Origins from an Azoxy-alkene-Producing Mutant of Streptomyces rochei 7434AN4

“…Streptomyces rochei 7434AN4 produces two polyketide antibiotics, lankacidin C and lankamycin (Figure S1), and harbors three characteristic linear plasmids: pSLA2-L, pSLA2-M, and pSLA2-S. − Our group focuses on their biosynthetic machinery − and the signaling-molecule-dependent regulatory mechanism. − In particular, our group has attempted the genome mining approaches through genetic manipulation on the signaling-molecule-dependent regulatory genes and the major biosynthetic pathways. Mutation of the lankacidin biosynthesis gene lkcA led to the accumulation of three polyketides: pentamycin, citreodiol, and epi -citreodiol .…”