Crystal structures of copper sensing bacterial histidine kinase
A. Cociurovscaia, G. Bujacz, A. Pietrzyk-Brzezińska
Institute of Molecular and Industrial Biotechnology, Lodz University of Technology
90-537 Lodz, Poland
anna.cociurovscaia@dokt.p.lodz.pl
The CusS histidine kinase is a component of the bacterial two-component signal transduction system CusS-CusR, engaged in Escherichia coli to prevent the damaging accumulation of copper ions [1]. The CusS, like classical histidine kinase, is a transmembrane multidomain protein [2]. It binds copper by the periplasmic sensor domain and propagates this signal toward the cytoplasmic catalytic core, through the coordinated conformational change of its subsequent domains. Then, the kinase core binds ATP, autophosphorylates its conserved histidine residue and transmits the γ-phosphoryl group to its cognate response regulator CusR. As a consequence, the response regulator binds to the target operon, responsible for the synthesis of copper-efflux pomp and regulates its transcription [3]. A small amount of copper ions is indispensable for aerobic cell metabolism. Nonetheless, its excess in the cytoplasm generates damaging reactive hydroxyl radicals [4]. For that reason, understanding bacterial copper sensing mechanisms can contribute to reducing bacterial resistance and developing bactericidal copper-based materials.
Using X-ray crystallography, the crystal structure of the CusS kinase core was solved at the resolution of 1.4 Å. The cytoplasmic catalytic domains ensemble in a homodimer structure. The CusS kinase core structure determination allowed us studying intramolecular and intermolecular interactions crucial for the mechanism of CusS autophosphorylation. Based on obtained structural data, conserved catalytic and structural motifs were identified and described. According to identified conserved motifs CusS can be classified into the Type I family of histidine kinases, the most common group of these enzymes constituting 72% of all histidine kinases.
Figure 1: (A) Protein crystals of CusS kinase obtained by hanging drop vapor diffusion technique.
(B) The overall structure of CusS catalytic kinase core.