Prestin, the Motor Protein of Cochlear Outer Hair Cells, and its Gene, Pres ( 99077b)
Researchers at Northwestern University have isolated a novel molecular motor molecule, Prestin, from outer hair cells (OHCs) of the mammalian cochlea. This unique biological motor is capable of direct, rapid, electro-mechanical conversion without dependence on ATP. The ability of this molecular motor to act as a transducer of electrical energy into mechanical activity at microsecond rates, suggests that this may be an ideal motor as part of nanomolecular assemblies or MEMS. Furthermore, prestin is a reciprocal motor, in response to mechanical deformation it generates charge displacement that can be measured as a voltage-dependent nonlinear capacitance. Consequently, prestin may function both as a nano-motor and as a nano-sensor.
SCIENTIFIC BACKGROUND: The sense organ for mammalian hearing is the cochlea, a coiled structure that responds to sound. Within the cochlea are sensory receptor cells that are divided into two distinct types, outer hair cells (OHCs) and inner hair cells (IHCs). Inner hair cells are responsible for conveying auditory information to the brain, while outer hair cells provide local mechanical amplification of sounds in the form of feedback. In response to electrical voltage changes caused by incoming sound vibrations, cylindrical outer hair cells rapidly alter their length and stiffness. These mechanical changes are assumed to produce amplification of vibrations in the cochlea that are then transduced by inner hair cells. Outer hair cells are responsible for the remarkable sensitivity and frequency resolving capacity of the mammalian ear.
The investigators believed that the mechanical changes observed in OHCs were driven by molecular motor molecules, located in the cells’ membranes, that perform direct, rapid, reversible electro-mechanical conversions. To isolate this molecular motor, the investigators analyzed the genetic makeup of outer and inner hair cells from gerbils and mice, and using modern molecular biological techniques, they isolated the gene and the motor protein, which they termed prestin, after the musical notation, presto. Prestin functions at remarkable speeds, altering cell length at the same rate as the frequency of an incoming sound (as much as 20,000 times per second). In addition, prestin is unique because it does not require an outside energy source (such as adenosine triphosphate, ATP) to function. Other well-known molecular motor molecules, such as dynein, kinesin, and myosin, are all based on enzymatic reactions, and they all require ATP to power their motion. In OHCs, however, sound stimulus produces electrical voltage changes in the outer hair cells that directly drive the molecular motor.
SUMMARY: Prestin, a biological motor that acts as a transducer of electrical energy into mechanical activity at microsecond rates and whose activity is independent of ATP, may be valuable in the emerging field of nanotechnology.
U. S. Patent No. 6,602,992 has issued and Northwestern University is interested in licensing this invention. The first page of the issued patent follows this abstract.
Peter Dallos, Jing Zheng, and Laird Madison
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