Myosin I Can Act As a Molecular Force Sensor
Joseph M. Laakso,
John H. Lewis,
Henry Shuman,
E. Michael Ostap*
The ability to sense molecular tension is crucial for a wide
array of cellular processes, including the detection of auditory
stimuli, control of cell shape, and internalization and transport
of membranes. We show that myosin I, a motor protein that has
been implicated in powering key steps in these processes, dramatically
alters its motile properties in response to tension. We measured
the displacement generated by single myosin I molecules, and
we determined the actin-attachment kinetics with varying tensions
using an optical trap. The rate of myosin I detachment from
actin decreases >75-fold under tension of 2 piconewtons or
less, resulting in myosin I transitioning from a low (<0.2)
to a high (>0.9) duty-ratio motor. This impressive tension
sensitivity supports a role for myosin I as a molecular force
sensor.
* To whom correspondence should be addressed at the Department of Physiology, University of Pennsylvania School of Medicine, B400 Richards Building, Philadelphia, PA 19104–6085, USA. E-mail: ostap{at}mail.med.upenn.edu
