POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
POSTERS - BLAST X - University of Utah
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<strong>BLAST</strong> X Poster #28<br />
TORQUE RESPONSE OF THE SODIUM-DRIVEN CHIMERIC FLAGELLAR MOTOR IN<br />
E.COLI INDUCED BY REVERSIBLE TEMPERATURE CHANGE<br />
Yuichi Inoue (1), Kuniaki Takeda (2), Hajime Fukuoka (1), Hiroto Takahashi (1) and Akihiko<br />
Ishijima (1).<br />
1: IMRAM, Tohoku <strong>University</strong>; 2: Graduate School <strong>of</strong> Life Sciences, Tohoku <strong>University</strong>, Katahira<br />
2-1-1, Aoba-ku, Sendai 980-8577, Japan<br />
Mechanical step <strong>of</strong> motor proteins is a key to understand the molecular mechanism <strong>of</strong><br />
energy transduction from chemical energy into mechanical work. We have demonstrated the 26<br />
steps in a rotation <strong>of</strong> Na + -driven chimeric flagellar motor (Sowa et al., 2005) and the torquespeed<br />
relationship (Inoue et al., 2008) using back-focal-plane interferometry. However, present<br />
time resolution is not enough to understand molecular mechanism <strong>of</strong> the steps <strong>of</strong> motor proteins<br />
including not only flagellar motors but also linear motors as skeletal myosin. One possible option<br />
would be to slow down the temperature-dependent processes in a chemo-mechanical cycle by<br />
reducing temperature.<br />
We report the cooling experiment with a water-cooling chip in a simple and reversible<br />
way. A small chip <strong>of</strong> ~18mm*18mm*2mm was made with glass cover slides and plastic tubes to<br />
lead cooling water. This chip was made direct contact on a sample chamber and placed in the<br />
light axis <strong>of</strong> the microscope. By changing temperature <strong>of</strong> the cooling flow, sample temperature<br />
from 23 to -8 degree Celsius was monitored using thermocouple. Temperature change could be<br />
applied repeatedly in a time constant < 60 sec.<br />
Simultaneous measurement <strong>of</strong> the motor speed and sample temperature showed the<br />
speed change as reported for low temperature (Chen and Berg, 2000). With increasing<br />
temperature with hot water, however, sudden drop <strong>of</strong> speed was measured over ~40 deg C.<br />
When the temperature returned back to room temperature, the speed was restored mostly in<br />
several minutes. The drop and recovery <strong>of</strong> the speed were coincided with stepwise change in<br />
the generated torque.<br />
These results suggest that our cooling system is useful not only for the cooling<br />
experiment for improving time resolution but also for the heating experiment to understand heat<br />
resistance which might be related to stator dynamics.<br />
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