Protein Friction Limits Diffusive and Directed Movements of Kinesin Motors on Microtubules
2009; American Association for the Advancement of Science; Volume: 325; Issue: 5942 Linguagem: Inglês
10.1126/science.1174923
ISSN1095-9203
AutoresVolker Bormuth, Vladimír Varga, Jonathon Howard, Erik Schäffer,
Tópico(s)Protein Structure and Dynamics
ResumoFriction limits the operation of macroscopic engines and is critical to the performance of micromechanical devices. We report measurements of friction in a biological nanomachine. Using optical tweezers, we characterized the frictional drag force of individual kinesin-8 motor proteins interacting with their microtubule tracks. At low speeds and with no energy source, the frictional drag was related to the diffusion coefficient by the Einstein relation. At higher speeds, the frictional drag force increased nonlinearly, consistent with the motor jumping 8 nanometers between adjacent tubulin dimers along the microtubule, and was asymmetric, reflecting the structural polarity of the microtubule. We argue that these frictional forces arise from breaking bonds between the motor domains and the microtubule, and they limit the speed and efficiency of kinesin.
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