The long term goal of this continuing research program is to understand the activation of receptors and kinases on a molecular level in their native environment. A molecular understanding of receptor on-off switching, adaptation, and kinase regulation has not yet been achieved for any signaling pathway, despite the fact these events control essential cell processes in all organisms. Such understanding is crucial to a basic knowledge of biological signaling circuits, and to medical applications seeking to block or modify these circuits. The project focuses on the bacterial chemosensory pathway, which assembles to form an ultrasensitive, ultrastable, multi-protein array and is the prototype for the large superfamily of two-component signaling systems ubiquitous in bacteria and lower eukaroytes. In particular, the project examines an active, membrane-bound core complex that is the minimal functional unit of the full sensory array. This core complex contains the chemoreceptor, its associated histidine kinase CheA, and the coupling protein CheW.
The Specific Aims will determine core complex architecture, will define the molecular mechanisms of receptor and kinase on-off switching, and will elucidate molecular interactions responsible for the ultrasensitivity and ultrastability of the signaling array. In addition, innovative site-directed cysteine chemistries and spectroscopic strategies are developed to probe structure and mechanism of the active signaling array in its native membrane environment.

Public Health Relevance

The components of the E. coli chemotaxis pathway assemble to form a biological integrated circuit typical of most bacterial signaling circuits. This simple circuit is medically important as a screening system for new broad-spectrum antibiotics. Moreover, it is the first signaling circuit found to be ultrastable, providing a platform for understanding ultrastability and for designing new ultrastable biosensors.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Biochemistry and Biophysics of Membranes Study Section (BBM)
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Flicker, Paula F
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University of Colorado at Boulder
Schools of Arts and Sciences
United States
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Parkinson, John S; Hazelbauer, Gerald L; Falke, Joseph J (2015) Signaling and sensory adaptation in Escherichia coli chemoreceptors: 2015 update. Trends Microbiol 23:257-66
Briegel, Ariane; Wong, Margaret L; Hodges, Heather L et al. (2014) New insights into bacterial chemoreceptor array structure and assembly from electron cryotomography. Biochemistry 53:1575-85
Briegel, Ariane; Wong, Margaret L; Hodges, Heather L et al. (2014) Correction to new insights into bacterial chemoreceptor array structure and assembly from electron cryotomography. Biochemistry 53:6624
Falke, Joseph J; Piasta, Kene N (2014) Architecture and signal transduction mechanism of the bacterial chemosensory array: progress, controversies, and challenges. Curr Opin Struct Biol 29:85-94
Piasta, Kene N; Falke, Joseph J (2014) Increasing and decreasing the ultrastability of bacterial chemotaxis core signaling complexes by modifying protein-protein contacts. Biochemistry 53:5592-600
Falke, Joseph J (2014) Piston versus scissors: chemotaxis receptors versus sensor His-kinase receptors in two-component signaling pathways. Structure 22:1219-1220
Li, Xiaoxiao; Fleetwood, Aaron D; Bayas, Camille et al. (2013) The 3.2 Å resolution structure of a receptor: CheA:CheW signaling complex defines overlapping binding sites and key residue interactions within bacterial chemosensory arrays. Biochemistry 52:3852-65
Natale, Andrew M; Duplantis, Jane L; Piasta, Kene N et al. (2013) Structure, function, and on-off switching of a core unit contact between CheA kinase and CheW adaptor protein in the bacterial chemosensory array: A disulfide mapping and mutagenesis study. Biochemistry 52:7753-65
Piasta, Kene N; Ulliman, Caleb J; Slivka, Peter F et al. (2013) Defining a key receptor-CheA kinase contact and elucidating its function in the membrane-bound bacterial chemosensory array: a disulfide mapping and TAM-IDS Study. Biochemistry 52:3866-80
Slivka, Peter F; Falke, Joseph J (2012) Isolated bacterial chemosensory array possesses quasi- and ultrastable components: functional links between array stability, cooperativity, and order. Biochemistry 51:10218-28

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