CHEMORECEPTORS: CONSERVED DESIGN FOR THE DETECTION OF MULTIPLE SIGNALS

STUDDERT, CA

Potrero de los Funes, San Luis

Congreso; XLVII Reunión Anual de SAIB; 2011

SAIB

Bacteria seek for favorable conditions by modulating their swimming mode in response to environmental signals. Chemoreceptors detect changes in the concentration of a great variety of chemicals and transmit the information to the flagellar motors through a phosphorylation cascade. We are interested in the architecture of the large signaling arrays composed by chemoreceptors of different specificities and their associated signaling proteins. These arrays are typically located at the poles of the cell and are very well conserved in prokaryotes. With a relatively simple design, they are capable of remarkable sensitivity along a broad operation range. The cytoplasmic domain of chemoreceptors consists in a long alpha-helical hairpin that forms, in the dimer, a coiled-coil fourhelix bundle. Chemoreceptors from different microorganisms share the basic structure but differ in the length of the cytoplasmic domain. In our laboratory, in vivo crosslinking approaches have been used to elucidate the precise arrangement of the signaling complexes. In E.coli cells, we analyze the signaling abilities and higher order organization of complexes containing native receptors, as well as receptors belonging to different classes or engineered receptors with an altered cytoplasmic domain. The ability of heterologous receptors to form active signaling complexes with E.coli proteins highlights the striking conservation of the pathway and opens a way towards the elucidation of the specificity of hundreds of uncharacterized receptors present in nature.