IIB   20738
INSTITUTO DE INVESTIGACIONES BIOLOGICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Independent signaling through separated chemoreceptyor arrays in Escherichia coli
Autor/es:
HERRERA SEITZ, M.K.; FRANK V; MASSAZZA, D. A.; VAKNIN, A; STUDDERT, C.A.
Lugar:
Mar del Plata
Reunión:
Congreso; X Reunión Anual de SAMIGE (Sociedad Argentina de Microbiología General); 2014
Institución organizadora:
SAMIGE
Resumen:
Bacterial chemotaxis allows microorganisms to move following chemical gradients in order to find optimal conditions to live in. The information from the environment is transmitted through the bacterial chemoreceptors that, interacting with CheA kinase and CheW coupling protein, are able to translate the signals into changes in the rotation of flagellar motors. Chemoreceptors usually have an extracellular ligand binding domain and a highly conserved cytoplasmic domain that consists in an alpha-helical hairpin and forms in the homodimer a coiled-coil four-helix bundle. E. coli chemoreceptors from different specificities form mixed trimers of dimers that are assembled together in a stable array and signal in a collaborative fashion. Symmetric insertions/deletions in both arms of the hairpin that occurred during evolution originated chemoreceptors that differ in the length of their cytoplasmic domain and can be grouped into seven different families. Many bacterial species code for chemoreceptors that belong to two or more different classes, but how these receptors are organized in the cell remains as an open question. To analyze the behavior of cells expressing chemoreceptors of different families, we engineered Tsr, the serine chemoreceptor of E. coli, through the introduction of symmetric 14-residue insertions. After random mutagenesis of this construct we obtained two functional Tsr derivatives with a significantly longer cytoplasmic domain. The aim of this work was to analyze the organization and signaling abilities of two chemoreceptors of different classes when they are co-expressed in the same cell. Functional analyses of the Tsr derivatives showed that they were able to control CheA in response to serine and localized to the poles of the cells as determined by fluorescent microscopy with CheZ-YFP and CheA-YFP analysis. Crosslinking experiments showed that the longer Tsr does not form mixed trimers of dimers with native Tar (aspartate sensing) E. coli chemoreceptor. Fluorescence anisotropy analysis further suggests that the longer Tsr does not incorporate efficiently in the same cluster with native Tar. The responses to serine and aspartate in cells co-expressing both receptors were analyzed by a FRET-based in vivo assay. Whereas cells expressing native Tar and Tsr signal collaboratively in response to aspartate and serine, cells expressing long Tsr and native Tar show independent responses to their ligands, suggesting that the two receptors of different lengths assemble into separate complexes that signal independently. Our results indicate that bacteria coding receptors from different families might sort them into different complexes, spatial or temporally separated from each other.