Understanding Molecular Motor Walking along a Microtubule: A Themosensitive Asymmetric Brownian Motor Driven by Bubble Formation

The “asymmetric Brownian ratchet
model”, a variation of Feynman’s ratchet and pawl system,
is invoked to understand the kinesin walking behavior along a microtubule.
The model system, consisting of a motor and a rail, can exhibit two
distinct binding states, namely, the random Brownian state and the
asymmetric potential state. When the system is transformed back and
forth between the two states, the motor can be driven to “walk”
in one direction. Previously, we suggested a fundamental mechanism,
that is, bubble formation in a nanosized channel surrounded by hydrophobic
atoms, to explain the transition between the two states. In this study,
we propose a more realistic and viable switching method in our computer
simulation of molecular motor walking. Specifically, we propose a
thermosensitive polymer model with which the transition between the
two states can be controlled by temperature pulses. Based on this
new motor system, the stepping size and stepping time of the motor
can be recorded. Remarkably, the “walking” behavior
observed in the newly proposed model resembles that of the realistic
motor protein. The bubble formation based motor not only can be highly
efficient but also offers new insights into the physical mechanism
of realistic biomolecule motors.