Protein exchange dynamics at chemoreceptor clusters in Escherichia coli.
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.
Schulmeister
Sonja
S
Zentrum für Molekulare Biologie and Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Universität Heidelberg, D-69120 Heidelberg, Germany.
Ruttorf
Michaela
M
Thiem
Sebastian
S
Kentner
David
D
Lebiedz
Dirk
D
Sourjik
Victor
V
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
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D011993:Recombinant Fusion Proteins