1. Identification of a Kinase-Active CheA Conformation in Escherichia coli Chemoreceptor Signaling Complexes
- Author
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John S. Parkinson and Germán E. Piñas
- Subjects
Models, Molecular ,Protein Conformation, alpha-Helical ,Histidine Kinase ,Amino Acid Motifs ,Static Electricity ,Mutant ,Methyl-Accepting Chemotaxis Proteins ,Biology ,Microbiology ,03 medical and health sciences ,Escherichia coli ,Protein Interaction Domains and Motifs ,Phosphorylation ,Kinase activity ,Molecular Biology ,030304 developmental biology ,chemistry.chemical_classification ,0303 health sciences ,Binding Sites ,Chemotaxis ,Escherichia coli Proteins ,030302 biochemistry & molecular biology ,Histidine kinase ,Autophosphorylation ,Gene Expression Regulation, Bacterial ,Transmembrane protein ,Amino acid ,Förster resonance energy transfer ,Amino Acid Substitution ,chemistry ,Mutation ,Mutagenesis, Site-Directed ,Biophysics ,bacteria ,Protein Conformation, beta-Strand ,Protein Multimerization ,biological phenomena, cell phenomena, and immunity ,Research Article ,Protein Binding ,Signal Transduction - Abstract
Escherichia coli chemotaxis relies on control of the autophosphorylation activity of the histidine kinase CheA by transmembrane chemoreceptors. Core signaling units contain two receptor trimers of dimers, one CheA homodimer, and two monomeric CheW proteins that couple CheA activity to receptor control. Core signaling units appear to operate as two-state devices, with distinct kinase-on and kinase-off CheA output states whose structural nature is poorly understood. A recent all-atom molecular dynamic simulation of a receptor core unit revealed two alternative conformations, “dipped” and “undipped,” for the ATP-binding CheA.P4 domain that could be related to kinase activity states. To explore possible signaling roles for the dipped CheA.P4 conformation, we created CheA mutants with amino acid replacements at residues (R265, E368, and D372) implicated in promoting the dipped conformation and examined their signaling consequences with in vivo Förster resonance energy transfer (FRET)-based kinase assays. We used cysteine-directed in vivo cross-linking reporters for the dipped and undipped conformations to assess mutant proteins for these distinct CheA.P4 domain configurations. Phenotypic suppression analyses revealed functional interactions among the conformation-controlling residues. We found that structural interactions between R265, located at the N terminus of the CheA.P3 dimerization domain, and E368/D372 in the CheA.P4 domain played a critical role in stabilizing the dipped conformation and in producing kinase-on output. Charge reversal replacements at any of these residues abrogated the dipped cross-linking signal, CheA kinase activity, and chemotactic ability. We conclude that the dipped conformation of the CheA.P4 domain is critical to the kinase-active state in core signaling units. IMPORTANCE Regulation of CheA kinase in chemoreceptor arrays is critical for Escherichia coli chemotaxis. However, to date, little is known about the CheA conformations that lead to the kinase-on or kinase-off states. Here, we explore the signaling roles of a distinct conformation of the ATP-binding CheA.P4 domain identified by all-atom molecular dynamics simulation. Amino acid replacements at residues predicted to stabilize the so-called “dipped” CheA.P4 conformation abolished the kinase activity of CheA and its ability to support chemotaxis. Our findings indicate that the dipped conformation of the CheA.P4 domain is critical for reaching the kinase-active state in chemoreceptor signaling arrays.
- Published
- 2019