CrossRef enabled

PAC Archives

Archive →

Pure Appl. Chem., 2011, Vol. 83, No. 9, pp. 1675-1684

Published online 2011-05-16

Conformational changes at the nucleotide pocket of motor proteins monitored by electron paramagnetic resonance spectroscopy

Nariman Naber1*, Roger Cooke2,1 and Edward Pate3

1 Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158, USA
2 Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA
3 Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA

Abstract: A fundamental goal in the field of motor proteins is to identify the conformational changes associated with the hydrolysis of the physiological substrate, ATP, and to define how these conformational changes are modulated by binding to the polymer track and translated into biologically useful movement. We have used electron paramagnetic resonance (EPR) spectroscopy to monitor conformational changes at the nucleotide-binding site of myosin- and kinesin-family motors. A novel set of nucleotide-analog EPR spin probes were synthesized and used to localize a spin moiety at the nucleotide site. This allows a reporter group to be placed with high specificity at the ATP binding site. Our results indicate that the nucleotide-binding site of myosin motors opens when the motor binds to its polymer roadway, actin, while that of kinesin closes on binding to microtubules (MTs). However, the transition is not all-or-none. There is instead an equilibrium between open and closed conformations. The different conformational changes in the two motor families can be correlated with differences in their biochemical cycles. Thus, we can now define the relationship between nucleotide-site structure, biochemistry and polymer binding for the two motors.