Polar Location of the Chemoreceptor Complex in the Escherichia coli Cell

Abstract

The eukaryotic cell exhibits compartmentalization of functions to various membrane-bound organelles and to specific domains within each membrane. The spatial distribution of the membrane chemoreceptors and associated cytoplasmic chemotaxis proteins in Escherichia coli were examined as a prototypic functional aggregate in bacterial cells. Bacterial chemotaxis involves a phospho-relay system brought about by ligand association with a membrane receptor, culminating in a switch in the direction of flagellar rotation. The transduction of the chemotaxis signal is initiated by a chemoreceptor-CheW-CheA ternary complex at the inner membrane. These ternary complexes aggregate predominantly at the cell poles. Polar localization of the cytoplasmic CheA and CheW proteins is dependent on membrane-bound chemoreceptor. Chemoreceptors are not confined to the cell poles in strains lacking both CheA and CheW. The chemoreceptor-CheW binary complex is polarly localized in the absence of CheA, whereas the chemoreceptor-CheA binary complex is not confined to the cell poles in strains lacking CheW. The subcellular localization of the chemotaxis proteins may reflect a general mechanism by which the bacterial cell sequesters different regions of the cell for specialized functions.

Bacterial chemoreceptors: high-performance signaling in networked arrays

“…Membrane-associated patches of ternary signaling complexes, containing chemoreceptors, the CheA histidine kinase and the coupling protein, CheW, were first detected by immunogold labeling of fixed, sectioned cells [18], later by imaging of fluorescently tagged chemotaxis proteins in living cells [8,19] and most recently by electron tomography of intact cells in vitreous ice [20]. All three methods detect no more than a few patches per cell, with most (~80%) located at a cell pole, although not at any particular position along the polar membrane.…”

Synthetic Multivalent Ligands as Probes of Signal Transduction

“…Data from microscopy, covalent cross-linking, and x-ray crystallography experiments have revealed that cell surface receptors from many structural classes assemble into multi-receptor complexes; these include some heptahelical G-protein coupled receptors (GPCRs), [36][37][38] methyl-accepting chemotaxis proteins (MCPs), [39] gated ion channels, [40] receptor protein tyrosine kinases (RPTKs), [41,42] and multichain immune recognition receptors (MIRRs). [22,33,35,[43][44][45] The size of these ensembles varies: Some complexes are composed of two receptors while others contain thousands.…”

“…[22,33,35,[43][44][45] The size of these ensembles varies: Some complexes are composed of two receptors while others contain thousands. Some receptors, [46][47][48] including the ryanodine receptor [40] and MCPs, [39] are so highly concentrated that they dominate certain subcellular regions. Unfortunately, little is known about the structures of these assemblies, where they are localized within the cells, and how their localization influences signaling.…”

“…[26,60,226,227] [54] Interestingly, the MCPs are organized within the cell: They are concentrated at the poles of Escherichia coli and other bacterial species. [39,228] This organization of chemoreceptors into an array has been proposed to be important in signal transduction. Recent experiments using synthetic multivalent ligands and other approaches support such a view; they suggest that communication between homologous and heterologous MCPs within the chemoreceptor array is responsible for chemotactic responses.…”

Compartmentalized distribution of the proteins controlling the prespore‐specific transcription factor σF of Bacillus subtilis

“…We have therefore applied newly developed immunofluorescence microscopic methods (Maddock & Shapiro 1993;Harry et al 1995;Pogliano et al 1995) to study the accumulation and cellular distribution of j F and its regulators during sporulation. Using affinity-purified antisera we have been able to visualize j F , SpoIIAB and the phosphorylated and non-phosphorylated forms of SpoIIAA.…”