Receptor sensitivity in bacterial chemotaxis

AUTOR(ES)

Sourjik, Victor

FONTE

The National Academy of Sciences

RESUMO

Chemoreceptors in Escherichia coli are coupled to the flagella by a labile phosphorylated intermediate, CheY∼P. Its activity can be inferred from the rotational bias of flagellar motors, but motor response is stochastic and limited to a narrow physiological range. Here we use fluorescence resonance energy transfer to monitor interactions of CheY∼P with its phosphatase, CheZ, that reveal changes in the activity of the receptor kinase, CheA, resulting from the addition of attractants or repellents. Analyses of cheR and/or cheB mutants, defective in receptor methylation/demethylation, show that response sensitivity depends on the activity of CheB and the level of receptor modification. In cheRcheB mutants, the concentration of attractant that generates a half-maximal response is equal to the dissociation constant of the receptor. In wild-type cells, it is 35 times smaller. This amplification, together with the ultrasensitivity of the flagellar motor, explains previous observations of high chemotactic gain.

Documentos Relacionados

• Receptor interactions through phosphorylation and methylation pathways in bacterial chemotaxis.
• Quantitative modeling of sensitivity in bacterial chemotaxis: The role of coupling among different chemoreceptor species
• Compensatory mutations in receptor function: a reevaluation of the role of methylation in bacterial chemotaxis.
• Adaptation kinetics in bacterial chemotaxis.
• Response tuning in bacterial chemotaxis