Abstract

In Streptomyces griseus, A-factor (2-isocapryloyl-3R-hydroxymethyl-gamma-butyrolactone) acts as a chemical signalling molecule that triggers morphological differentiation and secondary metabolism. A transcriptional activator, AdpA, in the A-factor regulatory cascade switches on a number of genes required for both processes, thus forming an AdpA regulon. amfR encoding a regulatory protein similar to response regulators of bacterial two-component regulatory systems and essential for aerial mycelium formation was found to be a member of the AdpA regulon. AdpA bound two sites at nucleotide positions approximately -200 (site 1) and -60 (site 2), with respect to the major transcriptional start point of amfR, and accelerated the transcription of amfR by assisting RNA polymerase in forming an open complex at an appropriate region including the transcriptional start point. Site 2 contributed more to the transcriptional activation of amfR by AdpA than site 1, although AdpA showed a much lower affinity to site 2 than to site 1. The amfR transcription enhanced by AdpA subsequently ceased at day 2 when aerial hyphae began to be formed in the wild-type strain, whereas in an adsA null mutant amfR was continuously transcribed even until day 3. This implied that amfR was repressed growth dependently by a gene product under the control of sigma-AdsA. Transcription of the promoter upstream of amfT depended on amfR, which is consistent with the idea that AmfR serves as an activator for amfTSBA in the amf operon. The observations that the amfR gene contains a TTA codon, a potential target for bldA-mediated regulation, and a conserved Asp-54 residue, which might be phosphorylated by a sensor kinase, suggest that the amf operon is under transcriptional, translational and post-translational control systems.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.