Mechanical Properties of Single Motor Molecules Studied by Three-Dimensional Thermal Force Probing in Optical Tweezers

• Published in: Chemphyschem Vol. 5; no. 8; pp. 1150 - 1158
• Main Authors: Jeney, Sylvia, Stelzer, Ernst H. K., Grubmüller, Helmut, Florin, Ernst-Ludwig
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 20.08.2004; WILEY‐VCH Verlag
• Subjects: mechanical properties; molecular motors; optical tweezers; single-molecule studies; thermal fluctuations
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.200301027

A new method combining three‐dimensional (3D) force measurements in an optical trap with the analysis of thermally induced (Brownian) position fluctuations of a trapped probe was used to investigate the mechanical properties of a single molecule, the molecular motor kinesin. One kinesin molecule attached to the probe was bound in a rigorlike state to one microtubule. The optical trap was kept weak to measure the thermal forces acting on the probe, which were mainly counterbalanced by the kinesin tether. The stiffness of kinesin during stretching and compression with respect to its backbone axis were measured. Our results indicate that a section of kinesin close to the motor domain is the dominating element in the flexibility of the motor structure. The experiments demonstrate the power of 3D thermal fluctuation analysis to characterize mechanical properties of individual motor proteins and indicate its usefulness to study single molecule in general. Thermal forces do it all. A novel method based on optical tweezers, 3D position detection and thermal noise analysis provides detailed information about protein nanomechanics in three dimensions and at minimal external forces (≪pN). Here the flexibility of the motility‐determining part of the molecular motor kinesin was studied while it was bound to a microtubule (see picture).