Dresden 2006 – scientific programme

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AKB: Biologische Physik

AKB 14: Molecular Motors

AKB 14.2: Talk

Tuesday, March 28, 2006, 16:30–16:45, ZEU 255

Measurement of the distance that walking kinesin holds its cargo away from the microtubule surface — •Jacob Kerssemakers¹, Jonathon Howard¹, Henry Hess², and Stefan Diez¹ — ¹MPI of Molecular Cell Biology and Genetics, Dresden, Germany — ²University of Florida, Gainesville, USA

While much has been learnt about how the heads of kinesin step along a microtubule, little is known about the role that the rod and tail domains play in motility. The tail is thought to be involved in cargo-binding and in generating a compact, autoinhibited conformation, but the role of the rod is not known. Here, we have investigated the extension of the rod during active transport by measuring the height at which microtubules glide over a kinesin-coated surface in the presence of ATP. To perform height measurements with nanometer-precision we utilized fluorescence-interference-contrast (FLIC) microscopy, the principle of which is based on high-resolution interference effects if fluorescent objects are imaged in the vicinity of a reflecting surface. Utilizing a self-calibrating method, we determined the distance by which kinesin molecules lift gliding microtubules above the surface to be 19.3+/-0.8 nm (95% confidence). While significantly shorter than the contour length of the motor molecule, this value is consistent with the segmented structure of the molecule. We propose that the function of the rod is to hold cargo sufficiently far away from the surface of the microtubule so that transport is not interfered with by proteins bound to the microtubules or the organelles.