Motor protein potential

Using NLC as an indicator, it has been shown that several experimental parameters can affect the function of the motor protein. First, an increase in turgor pressure in the OHC shifts the NLC curve toward the depolarization side (Kakehata and Santos-Sacchi, 1995 Adachi et al., 2000). Second, stepwise elevations (from +40 to —120 mV) of the preconditioning membrane potential of the OHC also shift the NLC curve to the depolarization side (Santos-Sacchi et al., 1998). Finally, the peak voltage of NLC measured in isolated OHCs also shifts 20-25 mV rightward (depolarizing) when the environmental temperature is increased by 10°C (Santos-Sacchi and Huang, 1998). 

Santos-Sacchi J, Shen W, Zheng J, Dallos P. 2001. Effects of membrane potential and tension on prestin, the outer hair cell lateral membrane motor protein. 1 Physiol 531 661-666. 

Movement of the motor protein can be modeled by the Smoluchowski equation by assuming that the center of mass of the motor protein as a Brownian motion with the presence of a periodic energy potential ... 

In particular, elastic network models reproduce the local shape of the folding free energy landscape of a protein by an artificial effective potential that does not contain any information on the physical means by which such shape is obtained. Moreover, they intrinsically bias the global minimum to a selected conformation, and thus they are not capable to capture the protein conformational changes and exploration of multiple structural minima that may be required for exploitation of the protein function (for example, in motor proteins, transporters etc.). Finally, these models do not contain any information on the external potential of the proteins therefore, they cannot be in principle used to explore in detail interactions of proteins with the environment [i.e., with membranes, other proteins or ligands). 

Muscle contraction is initiated by a signal from a motor nerve. This triggers an action potential, which is propagated along the muscle plasma membrane to the T-tubule system and the sarcotubular reticulum, where a sudden large electrically excited release of Ca " into the cytosol occurs. Accessory proteins closely associated with actin (troponins T, I, and C) together with tropomyosin mediate the Ca -dependent motor command within the sarcomere. Other accessory proteins (titin, nebulin, myomesin, etc.) serve to provide the myofibril with both stability... 

The macroscopic rates measured by radiolabel experiments should not be taken to reflect maximum rates of the motors involved. As with mitochondrial transport, the net rate of slow component proteins reflects both the rate of actual movement and the fraction of a time interval that a structure is moving. The elongate shape of cytoskeletal structures and their potential for many interactions means that net displacements are discontinuous. If a structure is moving at a speed of 2 j,m/s, but on average only moves at that rate for one second out of every 100 seconds, then the average rate for the structure will translate to a net rate of only 0.02 pm/s [31]. 

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