Mechanism of the pH-induced conformational change in the sensor domain of the DraK Histidine kinase via the E83, E105, and E107 residues.

Kwon Joo Yeo,Jae Kyoung Lee,Eun-Gyeong Lee,Young-Soo Hong,Hae-Kap Cheong,Eunha Hwang,Jin-Wan Park,Sang-Yoon Kim,Eun-Hee Kim,Jun-Goo Jee,Hyo Jeong Kim,Ohsuk Kwon,Paul C Driscoll

doi:10.1371/journal.pone.0107168

Abstract

The DraR/DraK two-component system was found to be involved in the differential regulation of antibiotic biosynthesis in a medium-dependent manner; however, its function and signaling and sensing mechanisms remain unclear. Here, we describe the solution structure of the extracellular sensor domain of DraK and suggest a mechanism for the pH-dependent conformational change of the protein. The structure contains a mixed alpha-beta fold, adopting a fold similar to the ubiquitous sensor domain of histidine kinase. A biophysical study demonstrates that the E83, E105, and E107 residues have abnormally high pKa values and that they drive the pH-dependent conformational change for the extracellular sensor domain of DraK. We found that a triple mutant (E83L/E105L/E107A) is pH independent and mimics the low pH structure. An in vivo study showed that DraK is essential for the recovery of the pH of Streptomyces coelicolor growth medium after acid shock. Our findings suggest that the DraR/DraK two-component system plays an important role in the pH regulation of S. coelicolor growth medium. This study provides a foundation for the regulation and the production of secondary metabolites in Streptomyces.

Highlights

Bacteria of the genus Streptomyces are one of the most important groups of microorganisms for the production of a large variety of valuable secondary metabolites, including antibiotics, anti-tumor agents and immunosuppressants [1,2]
In the case of global regulators, many are members of the two-component system (TCS), which is the predominant signal transduction system employed by bacteria to sense and respond to environmental changes [7,8]
The extracellular sensor domain (ESD) (E83Q) mutant provides a significant improvement in spectral quality compared with the wild type

Summary

Introduction

Bacteria of the genus Streptomyces are one of the most important groups of microorganisms for the production of a large variety of valuable secondary metabolites, including antibiotics, anti-tumor agents and immunosuppressants [1,2]. Regulation of secondary metabolite biosynthesis involves complex interactions of pathway-specific and global regulators that activate or repress the expression of corresponding biosynthetic genes depending on various conditions. The TCS consists of a membrane-embedded histidine kinase (HK), containing an N-terminal sensor (or input) domain and a conserved cytoplasmic kinase domain, and its cognate response regulator (RR), containing an N-terminal receiver domain and a C-terminal output domain. The sensor domain of HK undergoes a conformational change resulting in phosphorylation of a conserved histidine in its cytoplasmic kinase domain. The phosphorylated RR modulates the expression of target genes through protein-DNA and proteinprotein interactions to sense and adapt to the stimuli [9,10]

Methods

Results

Conclusion