Abstract

The intracellular K+ level in bacteria is strictly controlled by K+ uptake and efflux systems. Among these, KdpFABC is a high-affinity K+ transporter system that is generally activated by the KdpDE two-component system in response to K+ limitation stress. However, the regulatory mechanism remains obscure in bacteria lacking the kdpDE genes. Here we report that the transcription of a kdpFABC operon is distinctively regulated by a cyclic diadenylate monophosphate (c-di-AMP) riboswitch located at the 5′-untranslated region of kdp transcript, and binding of c-di-AMP to the riboswitch promotes its intrinsic termination that blocks the kdpFABC transcription. Further, the intracellular c-di-AMP concentration was found to decrease under the K+ limitation stress, leading to transcriptional read-through over the terminator to allow kdpFABC expression. This regulatory element is found predominantly in the Bacillus cereus group and correlate well with the K+ and c-di-AMP homeostasis that affects a variety of crucial cellular functions.

Highlights

  • Transport protein KdpA, as well as a small accessory membrane protein KdpF13

  • We found a c-di-AMP riboswitch sequence upstream of kdp transcript (Fig. 1a), which has been predicted by a previous bioinformatic analysis[21], hinting that BMB171 may incorporate a novel K+ uptake regulatory system for the kdp operon expression

  • We examined the transcription of the kdp operon after knockout of KdpD by real-time quantitative PCR (RT-qPCR)

Read more

Summary

Introduction

Transport protein KdpA, as well as a small accessory membrane protein KdpF13. the kdpFABC operons and structures of K+ uptake transporters are diverse, the regulation mode of kdpFABC operon appears to be rather consistent, being activated through a KdpDE two-component system[14]. Recent studies have demonstrated that the second messenger cyclic diadenylate monophosphate (c-di-AMP) is a crucial regulator for controlling K+ homeostasis. It controls K+ transporter activity or expression by binding to a receptor protein such as KtrA, TrkA, KdpD, c-di-AMP binding protein CabP, or cation/proton antiporter CpaA15–17. As a genetic switch, binding of a specific ligand to the aptamer domain typically induces conformational changes in the expression platform, leading to different protein yield through transcriptional termination, activation/inhibition of translation initiation, or self-cleavage mechanism[21,22,23,24,25].

Methods
Results
Conclusion
Full Text
Published version (Free)

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