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primary topic: Adaptation and methylation kinetics in Escherichia coli chemotaxis

Adaptation and methylation kinetics in Escherichia coli chemotaxis
type: Article
abstract: Transmembrane chemoreceptors of Escherichia coli bind periplasmic ligands and transduce the signal to the flagella motors, thereby adjusting the swimming behaviour of the cell according to the chemical nature of the ligand. Cell movement, directed either towards nutrients or away from toxic compounds, is known as chemotaxis. An important property of the chemotaxis signalling pathway essential for navigation in complex gradients of nutrients is adaptation, mediated by methylation of specific glutamate residues in the chemoreceptors cytoplasmic domain. The aspartate chemoreceptor Tar possesses four such sites, but it is still unclear why several sites of methylation are needed and if a certain hierarchy among these sites exists. In this study, we systematically and quantitatively characterized the efficiency of chemotaxis and the precision of adaptation for cells expressing Tar mutated at one or more modification sites as the only chemoreceptor. Therefore, we constructed Tar chemoreceptors with all possible combinations of alanine substitutions at the methylation sites to specifically render them non-methylatable. These Tar mutants were then tested for their ability to mediate chemotaxis on soft agar plates. Furthermore, adaptation kinetics of Tar mutants were analyzed by in vivo FRET microscopy and wild-type Tar was investigated by mass spectrometrical analysis, which allows to follow the order and kinetics of methylation at individual modification sites during the adaptation process. We found that the receptor methylation rate following addition of attractant differs for the individual methylation sites with methylation site 2 being fastest, followed by sites 1 and 3, and site 4 having the slowest rate of methylation. Demethylation upon removal of attractant occurs first at methylation site 3, followed by sites 2 and 1. Furthermore, we discovered that specific methylation sites are responsible for different features of chemotaxis and adaptation. Methylation site 1 m…
date: 2014
author list: authors
type: EPrint
type: DoctoralThesisEPrint
is part of: repository
has document: Adaptation and methylation kinetics in Escherichia coli chemotaxis (PDF)
has document: Adaptation and methylation kinetics in Escherichia coli chemotaxis (Other)
subject: 570 Biowissenschaften, Biologie

Adaptation and methylation kinetics in Escherichia coli chemotaxis (PDF)
type: Document
has file: Thesis_Anna_UB.pdf
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Anna Katharina Krembel
type: Person
given name: Anna Katharina
family name: Krembel

Adaptation and methylation kinetics in Escherichia coli chemotaxis (Other)
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Adaptation and methylation kinetics in Escherichia coli chemotaxis (Other)
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Adaptation and methylation kinetics in Escherichia coli chemotaxis (Other)
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Adaptation and methylation kinetics in Escherichia coli chemotaxis (Other)
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Adaptation and methylation kinetics in Escherichia coli chemotaxis (Other)
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primary topic: Adaptation and methylation kinetics in Escherichia coli chemotaxis

570 Biowissenschaften, Biologie
type: Concept
preferred label: 570 Life sciences @en