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Conformational dynamics are a key factor in signaling mediated by the receiver domain of a sensor histidine kinase from Arabidopsis thaliana.

ABSTRACT: Multistep phosphorelay (MSP) cascades mediate responses to a wide spectrum of stimuli, including plant hormonal signaling, but several aspects of MSP await elucidation. Here, we provide first insight into the key step of MSP-mediated phosphotransfer in a eukaryotic system, the phosphorylation of the receiver domain of the histidine kinase CYTOKININ-INDEPENDENT 1 (CKI1RD) from Arabidopsis thaliana We observed that the crystal structures of free, Mg2+-bound, and beryllofluoridated CKI1RD (a stable analogue of the labile phosphorylated form) were identical and similar to the active state of receiver domains of bacterial response regulators. However, the three CKI1RD variants exhibited different conformational dynamics in solution. NMR studies revealed that Mg2+ binding and beryllofluoridation alter the conformational equilibrium of the ?3-?3 loop close to the phosphorylation site. Mutations that perturbed the conformational behavior of the ?3-?3 loop while keeping the active-site aspartate intact resulted in suppression of CKI1 function. Mechanistically, homology modeling indicated that the ?3-?3 loop directly interacts with the ATP-binding site of the CKI1 histidine kinase domain. The functional relevance of the conformational dynamics observed in the ?3-?3 loop of CKI1RD was supported by a comparison with another A. thaliana histidine kinase, ETR1. In contrast to the highly dynamic ?3-?3 loop of CKI1RD, the corresponding loop of the ETR1 receiver domain (ETR1RD) exhibited little conformational exchange and adopted a different orientation in crystals. Biochemical data indicated that ETR1RD is involved in phosphorylation-independent signaling, implying a direct link between conformational behavior and the ability of eukaryotic receiver domains to participate in MSP.

SUBMITTER: Otrusinova O

PROVIDER: S-EPMC5655527 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Conformational dynamics are a key factor in signaling mediated by the receiver domain of a sensor histidine kinase from Arabidopsis thaliana.

Otrusinová Olga O Demo Gabriel G Padrta Petr P Jaseňáková Zuzana Z Pekárová Blanka B Gelová Zuzana Z Szmitkowska Agnieszka A Kadeřávek Pavel P Jansen Séverine S Zachrdla Milan M Klumpler Tomáš T Marek Jaromír J Hritz Jozef J Janda Lubomír L Iwaï Hideo H Wimmerová Michaela M Hejátko Jan J Žídek Lukáš L

The Journal of biological chemistry 20170831 42

Multistep phosphorelay (MSP) cascades mediate responses to a wide spectrum of stimuli, including plant hormonal signaling, but several aspects of MSP await elucidation. Here, we provide first insight into the key step of MSP-mediated phosphotransfer in a eukaryotic system, the phosphorylation of the receiver domain of the histidine kinase CYTOKININ-INDEPENDENT 1 (CKI1RD) from Arabidopsis thaliana We observed that the crystal structures of free, Mg2+-bound, and beryll ...[more]

PMID: 28860196

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Project description:VxrA and VxrB are cognate histidine kinase (HK) - response regulator (RR) pairs of a two-component signaling system (TCS) found in Vibrio cholerae, a bacterial pathogen that causes cholera. The VxrAB TCS positively regulates virulence, the Type VI Secretion System, biofilm formation, and cell wall homeostasis in V. cholerae, providing protection from environmental stresses and contributing to the transmission and virulence of the pathogen. The VxrA HK has a unique periplasmic sensor domain (SD) and, remarkably, lacks a cytoplasmic linker domain between the second transmembrane helix and the dimerization and histidine phosphotransfer (DHp) domain, indicating that this system may utilize a potentially unique signal sensing and transmission TCS mechanism. In this study, we have determined several crystal structures of VxrA-SD and its mutants. These structures reveal a novel structural fold forming an unusual β hairpin-swapped dimer. A conformational change caused by relative rotation of the two monomers in a VxrA-SD dimer could potentially change the association of transmembrane helices and, subsequently, the pairing of cytoplasmic DHp domains. Based on the structural observation, we propose a putative scissor-like closing regulation mechanism for the VxrA HK.IMPORTANCE V. cholerae has a dynamic life cycle, which requires rapid adaptation to changing external conditions. Two-component signal transduction (TCS) systems allow V. cholerae to sense and respond to these environmental changes. The VxrAB TCS positively regulates a number of important V. cholerae phenotypes, including virulence, the Type Six Secretion System, biofilm formation, and cell wall homeostasis. Here, we provide the crystal structure of the VxrA sensor histidine kinase sensing domain and propose a mechanism for signal transduction. The cognate signal for VxrAB remains unknown, however, in this work we couple our structural analysis with functional assessments of key residues to further our understanding of this important TCS.

Dataset Information

Conformational dynamics are a key factor in signaling mediated by the receiver domain of a sensor histidine kinase from Arabidopsis thaliana.

Publications

Conformational dynamics are a key factor in signaling mediated by the receiver domain of a sensor histidine kinase from <i>Arabidopsis thaliana</i>.

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