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Engineering an Osmosensor by Pivotal Histidine Positioning within Disordered Helices.

ABSTRACT: Histidine kinases (HKs) funnel diverse environmental stimuli into a single autophosphorylation event at a conserved histidine residue. The HK EnvZ is a global sensor of osmolality and cellular acid pH. In previous studies, we discovered that osmosensing in EnvZ was mediated through osmolyte-induced stabilization of the partially disordered helical backbone spanning the conserved histidine autophosphorylation site (His243). Here, we describe how backbone stabilization leads to changes in the microenvironment of His243, resulting in enhanced autophosphorylation through relief of inhibition and repositioning of critical side chains and imidazole rotamerization. The conserved His-Asp/Glu dyad within the partially structured helix is equally geared to respond to acid pH, an alternative environmental stimulus in bacteria. This high-resolution "double-clamp" switch model proposes that a His-Asp/Glu dyad functions as an integrative node for regulating autophosphorylation in HKs. Because the His-Asp/Glu dyad is highly conserved in HKs, this study provides a universal model for describing HK function.

SUBMITTER: Ghosh M

PROVIDER: S-EPMC6377431 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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Engineering an Osmosensor by Pivotal Histidine Positioning within Disordered Helices.

Ghosh Madhubrata M Wang Loo Chien LC Huber Roland G RG Gao Yunfeng Y Morgan Leslie K LK Tulsian Nikhil Kumar NK Bond Peter J PJ Kenney Linda J LJ Anand Ganesh S GS

Structure (London, England : 1993) 20181129 2

Histidine kinases (HKs) funnel diverse environmental stimuli into a single autophosphorylation event at a conserved histidine residue. The HK EnvZ is a global sensor of osmolality and cellular acid pH. In previous studies, we discovered that osmosensing in EnvZ was mediated through osmolyte-induced stabilization of the partially disordered helical backbone spanning the conserved histidine autophosphorylation site (His<sup>243</sup>). Here, we describe how backbone stabilization leads to changes ...[more]

PMID: 30503779

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Project description:In plants, the multistep phosphorelay signaling pathway mediates responses to environmental factors and plant hormones. This system is composed of three successive partners: hybrid Histidine-aspartate Kinases (HKs), Histidine-containing Phosphotransfer proteins (HPts), and Response Regulators (RRs). Among the third partners, B-type RR family members are the final output elements of the pathway; they act as transcription factors and clearly play a pivotal role in the early response to cytokinin in Arabidopsis. While interactions studies between partners belonging to the multistep phosphorelay system are mainly focused on protagonists involved in cytokinin or ethylene pathways, very few reports are available concerning partners of osmotic stress signaling pathway.In Populus, we identified eight B-type RR proteins, RR12-16, 19, 21 and 22 in the Dorskamp genotype. To assess HPt/B-type RR interactions and consequently determine potential third partners in the osmosensing multistep phosphorelay system, we performed global yeast two-hybrid (Y2H) assays in combination with Bimolecular Fluorescence Complementation (BiFC) assays in plant cells. We found that all B-type RRs are able to interact with HPt predominant partners (HPt2, 7 and 9) of HK1, which is putatively involved in the osmosensing pathway. However, different profiles of interaction are observed depending on the studied HPt. HPt/RR interactions displayed a nuclear localization, while the nuclear and cytosolic localization of HPt and nuclear localization of RR proteins were validated. Although the nuclear localization of HPt/RR interaction was expected, this work constitutes the first evidence of such an interaction in plants. Furthermore, the pertinence of this partnership is reinforced by highlighting a co-expression of B-type RR transcripts and the other partners (HK1 and HPts) belonging to a potential osmosensing pathway.Based on the interaction studies between identified B-type RR and HPt proteins, and the co-expression analysis of transcripts of these potential partners in poplar organs, our results favor the model that RR12, 13, 14, 16 and 19 are able to interact with the main partners of HK1, HPt2, 7 and 9, and this HPt/RR interaction occurs within the nucleus. On the whole, the five B-type RRs of interest could be third protagonists putatively involved in the osmosensing signaling pathway in Populus.

Dataset Information

Engineering an Osmosensor by Pivotal Histidine Positioning within Disordered Helices.

Publications

Engineering an Osmosensor by Pivotal Histidine Positioning within Disordered Helices.

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