<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Adaptation and methylation kinetics in Escherichia coli chemotaxis"^^ . "Transmembrane chemoreceptors of Escherichia coli bind periplasmic ligands and transduce\r\nthe signal to the flagella motors, thereby adjusting the swimming behaviour of the cell according\r\nto the chemical nature of the ligand. Cell movement, directed either towards nutrients\r\nor away from toxic compounds, is known as chemotaxis. An important property of the\r\nchemotaxis signalling pathway essential for navigation in complex gradients of nutrients is\r\nadaptation, mediated by methylation of specific glutamate residues in the chemoreceptors\r\ncytoplasmic domain. The aspartate chemoreceptor Tar possesses four such sites, but it is\r\nstill unclear why several sites of methylation are needed and if a certain hierarchy among\r\nthese sites exists.\r\nIn this study, we systematically and quantitatively characterized the efficiency of chemotaxis\r\nand the precision of adaptation for cells expressing Tar mutated at one or more modification\r\nsites as the only chemoreceptor. Therefore, we constructed Tar chemoreceptors with all possible\r\ncombinations of alanine substitutions at the methylation sites to specifically render them\r\nnon-methylatable. These Tar mutants were then tested for their ability to mediate chemotaxis\r\non soft agar plates. Furthermore, adaptation kinetics of Tar mutants were analyzed by\r\nin vivo FRET microscopy and wild-type Tar was investigated by mass spectrometrical analysis,\r\nwhich allows to follow the order and kinetics of methylation at individual modification\r\nsites during the adaptation process. We found that the receptor methylation rate following\r\naddition of attractant differs for the individual methylation sites with methylation site 2 being\r\nfastest, followed by sites 1 and 3, and site 4 having the slowest rate of methylation.\r\nDemethylation upon removal of attractant occurs first at methylation site 3, followed by\r\nsites 2 and 1. Furthermore, we discovered that specific methylation sites are responsible for\r\ndifferent features of chemotaxis and adaptation. Methylation site 1 mainly contributes to the\r\nadaptation precision and the methylation rate, whereas methylation site 2 is important for\r\nthe methylation rate as well as for the demethylation rate. Methylation site 3 is responsible\r\nfor the chemotaxis and the demethylation rate and methylation site 4 mainly contributes to\r\nthe methylation rate.\r\nIn summary, the results of the present study provide new insights into the molecular details of\r\nthe adaptation process in E. coli chemotaxis and the subtle interplay of individual methylation\r\nsites in the regulation of chemotactic behavior."^^ . "2014" . . . . . . . "Anna Katharina"^^ . "Krembel"^^ . "Anna Katharina Krembel"^^ . . . . . . "Adaptation and methylation kinetics in Escherichia coli chemotaxis (PDF)"^^ . . . "Thesis_Anna_UB.pdf"^^ . . . "Adaptation and methylation kinetics in Escherichia coli chemotaxis (Other)"^^ . . . . . . "indexcodes.txt"^^ . . . "Adaptation and methylation kinetics in Escherichia coli chemotaxis (Other)"^^ . . . . . . "small.jpg"^^ . . . "Adaptation and methylation kinetics in Escherichia coli chemotaxis (Other)"^^ . . . . . . "medium.jpg"^^ . . . "Adaptation and methylation kinetics in Escherichia coli chemotaxis (Other)"^^ . . . . . . "preview.jpg"^^ . . . "Adaptation and methylation kinetics in Escherichia coli chemotaxis (Other)"^^ . . . . . . "lightbox.jpg"^^ . . "HTML Summary of #16712 \n\nAdaptation and methylation kinetics in Escherichia coli chemotaxis\n\n" . "text/html" . . . "570 Biowissenschaften, Biologie"@de . "570 Life sciences"@en . .