562015-03-24 , 法政大学大学院理工学・工学研究科
In the chemotaxis of Escherichia coli, four methyl-accepting chemotaxis proteins (MCPs), i.e. Tsr, Tar, Trg and Tap, mediate attractant and repellent responses to various chemicals and other stimuli. MCPs form clusters with the histidine kinase CheA and the adaptor CheW at a cell pole. Polar localization and clustering of the signaling proteins are critical for signal amplification and adaptation. However, little is known about the mechanisms underlying receptor localization itself. In this study, I focused on localization and dynamics of the aspartate chemoreceptor Tar. A series of mutants lacking chemotaxis signaling proteins were constructed from the strain expressing Tar fused to green fluorescent protein (Tar-GFP) from the chromosomal gene. In the cheA or cheW deletion backgrounds, Tar-GFP localized mostly to lateral regions of the membrane. Total internal reflection fluorescence microscopy revealed that some Tar-GFP foci are moving in the lateral region and their fluorescence intensities were distributed in a wide range, suggesting that they represent higher oligomers consisting of either Tar alone or mixed MCPs. The deletion of cheA and cheW shifted mildly or drastically shifted the distribution toward lower intensities, suggesting that MCP forms a complex with CheA and CheW in lateral regions of membrane.