Graduate School of Frontier Biosciences, Osaka University

Japanese

Colloquium 202

Speaker Hajime Fukuoka  (Associate professor / Laboratory of Nano-Biophysics (Ishijima Lab.))
Title "Measurement for the chemotaxis proteins and cellular behavior in single E. coli cel”
Speaker Tatsuki Hamamoto (Student of graduate school of FBS (D1) / Laboratory of Nano-Biophysics (Ishijima Lab.))
Title "Computational simulation of spontaneous transition between active and inactive in whole chemoreceptor array in E. coli.”
Date Wed., December 19, 2018, 12:15~13:00
Place 2F Seminar room, BioSystems Building
Host Contact:Hajime Fukuoka
Tel :06-6879-4429
E-mail:f-hajime@fbs.osaka-u.ac.jp












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Title/Abstract

"Measurement for the chemotaxis proteins and cellular behavior in single E. coli cel”

E.coli cells migrate toward favorable environments in response to extracellular signals by regulating the rotational direction of flagellar motors. This phenomenon is called chemotaxis system. Receptors modulate the autophosphorylation activity of CheA, and the phosphoryl group on CheA is rapidly transferred to a response regulator, CheY. Phosphorylated CheY (CheY-P) propagates in cytoplasm and binds to a motor to induce a switch of rotational direction of motor from a counterclockwise to a clockwise direction. Previous study in our laboratory proposed a model that the dynamic change in CheY-P concentration directly regulates the rotational switching of motors under steady-state in the absence of extracellular. If this model is true, the receptor array’s activity should be correlated with the rotational direction of motor because the activity of receptor generates CheY-P. To quantitatively understand this, the dynamics of chemotaxis proteins and the cellular response should be measured simultaneously at single cell. Therefore, we are trying to measure the change in the localization of CheY, the concentration of CheY-P, and/or the receptor’s activity detected thorough FRET technique, with motor rotation. In this colloquium, we will discuss our recent results about the signaling process based on experimental results measured at a single E. coli cell.

"Computational simulation of spontaneous transition between active and inactive in whole chemoreceptor array in E. coli.”

Recent our studies suggested the receptor array repeatedly change between active and inactive states without extracellular stimuli. To explain this behavior, we constructed the computational model for receptor array’s activity. Each receptor has active or inactive states, and both states has also methylated or not. We considered high cooperativity in receptor array; both active to inactive and inactive to active transition were affected by surrounding other receptors states. Our model show that the receptor array repeatedly changed between active and inactive states spontaneously and well fitted the average CW and CCW duration time. This model represents the inhibition of the cooperative manner by the insertion of receptor mutant, which was shown in experimentally.


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