Accounting for the energies and entropies of kinesin's catalytic cycle
Department of Physics, East Carolina University, Greenville, NC 27858, USA
Corresponding author: a firstname.lastname@example.org
Revised: 26 April 2008
Published online: 9 July 2008
When the processive motor protein kinesin walks along the biopolymer microtubule it can occasionally make a backward step. Recent single molecule experiments on moving kinesin have revealed that the forward-to-backward step ratio decreases exponentially with the load force. Carter and Cross (Nature 435, 308–312, 2005) found that this ratio tightly followed 802×exp[ -0.95 F] , where F is the load force in piconewtons. A straightforward analysis of a Brownian step leads to as the factor in front of the load force, where L is the 8 nm stepsize, kB is the Boltzmann constant, and T is the temperature. The factor does indeed equal 0.95 pN-1. The same analysis shows how the 802 prefactor derives from the power stroke energy G as exp[ G/(2 kB T)] . There are indications that the power stroke derives from the entropically driven coiling of the 30 amino acid neck linker that connects the two kinesin heads. This idea is examined and consequences are deduced.
PACS: 87.16.Nn – Motor proteins / 05.40.-a – Fluctuation phenomena, random processes, noise, and Brownian motion
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2008