title: Protein exchange dynamics at chemoreceptor clusters in Escherichia coli.
abstract: Signal processing in bacterial chemotaxis relies on large sensory complexes consisting of thousands of protein molecules. These clusters create a scaffold that increases the efficiency of pathway reactions and amplifies and integrates chemotactic signals. The cluster core in Escherichia coli comprises a ternary complex composed of receptors, kinase CheA, and adaptor protein CheW. All other chemotaxis proteins localize to clusters by binding either directly to receptors or to CheA. Here, we used fluorescence recovery after photobleaching (FRAP) to investigate the turnover of chemotaxis proteins at the cluster and their mobility in the cytoplasm. We found that cluster exchange kinetics were protein-specific and took place on several characteristic time scales that correspond to excitation, adaptation, and cell division, respectively. We further applied analytical and numerical data fitting to analyze intracellular protein diffusion and to estimate the rate constants of cluster equilibration in vivo. Our results indicate that the rates of protein turnover at the cluster have evolved to ensure optimal performance of the chemotaxis pathway.
authors.affiliation: Zentrum für Molekulare Biologie and Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Universität Heidelberg, D-69120 Heidelberg, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Schulmeister
authors.forename: Michaela
authors.initials: M
authors.lastname: Ruttorf
authors.forename: Sebastian
authors.initials: S
authors.lastname: Thiem
authors.forename: David
authors.initials: D
authors.lastname: Kentner
authors.forename: Dirk
authors.initials: D
authors.lastname: Lebiedz
authors.forename: Victor
authors.initials: V
authors.lastname: Sourjik
mesh_terms: D001426:Bacterial Proteins; D002628:Chemoreceptor Cells / Q000378:metabolism*; D002633:Chemotaxis; D004058:Diffusion; D004926:Escherichia coli / Q000166:cytology / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D036681:Fluorescence Recovery After Photobleaching; D007700:Kinetics; D011485:Protein Binding; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D011993:Recombinant Fusion Proteins