Thompson, Lynmarie

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Associate Professor, Department of Chemistry
Last Name
Thompson
First Name
Lynmarie
Discipline
Chemistry
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Introduction
Principal Research Interests
Membrane proteins are key players in the essential cellular processes of energy and signal transduction. Our laboratory is interested in understanding the molecular mechanisms of such processes: How does a membrane receptor transmit a signal across the membrane? How does a transporter use the energy of ATP hydrolysis to drive transport across the membrane? Such molecules and processes are of both fundamental and medical interest.
The transmembrane receptors of bacterial chemotaxis bind specific attractant molecules and transmit this information across the membrane to direct the swimming of the bacterium. Both receptor conformational changes and receptor clusters are known to be important in the signaling mechanism. As with most membrane proteins, the traditional tools of structural biology have not been able to provide structures of the intact receptor to measure and follow the ligand-induced conformational changes. We have used a powerful site-directed distance measurement strategy to measure helix-helix distances in the periplasmic domain of the intact serine receptor that are consistent in magnitude with a proposed ligand-induced piston mechanism. Additional distance measurements are in progress to test structural models of the receptor clusters. Companion biochemical experiments are testing the role of receptor clustering in the signaling mechanism. In collaboration with Robert Weis’ lab, we are applying a number of biochemical and biophysical approaches to receptor arrays to provide a molecular picture of how a protein transmits a signal across a membrane.
ABC transporters are a large family of proteins that use the energy of ATP hydrolysis to drive transport of molecules into or out of the cell. Recent crystal structures of these proteins are providing new insights into proposed alternating access mechanisms of transport. We have initiated a new project to establish correlations between activity changes and structural changes, with the goal of understanding how ATP hydrolysis is coupled to the conformational changes that transport the substrate across the membrane.
Our overall strategy is to combine biophysical experiments including emerging solid-state NMR methods with biochemical approaches to probe the structure and mechanism of membrane proteins. Membrane proteins are both tremendously important (as pharmaceutical targets for example) and poorly understood, making this an area rich in opportunities for exciting research.
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  • Publication
    Bacterial chemoreceptor signaling complexes control kinase activity by stabilizing the catalytic domain of CheA
    (2023-01) Tran, Thomas; Karunanayake Mudiyanselage, Aruni PKK; Eyles, Stephen J.; Thompson, Lynmarie K
    Motile bacteria have a chemotaxis system that enables them to sense their environment and direct their swimming toward favorable conditions. Chemotaxis involves a signaling process in which ligand binding to the extracellular domain of the chemoreceptor alters the activity of the histidine kinase, CheA, bound ~300 Å away to the distal cytoplasmic tip of the receptor, to initiate a phosphorylation cascade that controls flagellar rotation. The cytoplasmic domain of the receptor is thought to propagate this signal via changes in dynamics and/or stability, but it is unclear how these changes modulate the kinase activity of CheA. To address this question, we have used hydrogen deuterium exchange mass spectrometry to probe the structure and dynamics of CheA within functional signaling complexes of the Escherichia coli aspartate receptor cytoplasmic fragment, CheA, and CheW. Our results reveal that stabilization of the P4 catalytic domain of CheA correlates with kinase activation. Furthermore, differences in activation of the kinase that occur during sensory adaptation depend on receptor destabilization of the P3 dimerization domain of CheA. Finally, hydrogen exchange properties of the P1 domain that bears the phosphorylated histidine identify the dimer interface of P1/P1’ in the CheA dimer and support an ordered sequential binding mechanism of catalysis, in which dimeric P1/P1’ has productive interactions with P4 only upon nucleotide binding. Thus stabilization/destabilization of domains is a key element of the mechanism of modulating CheA kinase activity in chemotaxis, and may play a role in the control of other kinases.