論文 - 森本　雄祐

Role of a Conserved Prolyl Residue (Pro173) of MotA in the Mechanochemical Reaction Cycle of the Proton-Driven Flagellar Motor of Salmonella 査読有り 国際誌

Nakamura S., Morimoto Y., Kami-ike N., Minamino T., Namba K.

Journal of Molecular Biology   393 ( 2 )   300 - 307   2009年10月

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

The MotA/B complex acts as the stator of the proton-driven bacterial flagellar motor. Proton translocation through the stator complex is efficiently coupled with torque generation by the stator-rotor interactions. In Salmonella enterica serovar Typhimurium, the highly conserved Pro173 residue of MotA is close to the absolutely conserved Asp33 residue of MotB, which is believed to be a proton-binding site. Pro173 is postulated to be involved in coupling proton influx to torque generation. However, it remains unknown what critical function Pro173 carries out. Here, we characterize the motility and the torque-speed relation of the flagellar motor of the slow motile motA(P173A) mutant of Salmonella. Stall torque produced by the mutant motor was at the wild-type level, indicating that neither the number of stators in the motor nor the rotor-stator interaction is affected by the P173A substitution. In agreement with this, the motA(P173A) allele exerted a strong dominant-negative effect on wild-type motility. In contrast, high-speed rotation at low load was significantly impaired by the mutation, suggesting that the maximum rate of torque generation cycle is severely limited. Simulation of the torque-speed curve by a simple kinetic model indicated that the mutation reduces the rate of conformational changes of the MotA/B complex that switches the exposure of Asp33 to the outside and the inside of the cell, thereby slowing down the mechanochemical reaction cycle. Based on these results, we propose that Pro173 plays an important role in facilitating the conformational dynamics of the stator complex for rapid proton translocation and torque generation cycle. © 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jmb.2009.08.022

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Antennal motor activity induced by pilocarpine in the American cockroach 査読有り 国際誌

Okada J., Morimoto Y., Toh Y.

Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology   195 ( 4 )   351 - 363   2009年01月

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The antennal motor system is activated by the muscarinic agonist pilocarpine in the American cockroach Periplaneta americana, and its output patterns were examined both in restrained intact animals and in isolated CNS preparations. The three-dimensional antennal movements induced by the hemocoelic drug injection were analyzed in in vivo preparations. Pilocarpine effectively induced prolonged rhythmic movements of both antennae. The antennae tended to describe a spatially patterned trajectory, forming loops or the symbol of infinity (∞). Such spatial regularity is comparable to that during spontaneous tethered-walking. Rhythmic bursting activities of the antennal motor nerves in in vitro preparations were also elicited by bath application of pilocarpine. Cross-correlation analyses of the bursting spike activities revealed significant couplings among certain motor units, implying the spatial regularity of the antennal trajectory. The pilocarpine-induced rhythmic activity of antennal motor nerves was effectively suppressed by the muscarinic antagonist atropine. These results indicate that the activation of the antennal motor system is mediated by muscarinic receptors. © 2009 Springer-Verlag.

DOI： 10.1007/s00359-008-0411-6

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