Prof. Paul Selvin, Loomis Lab of Physics, University of Illinois
Single Molecule Fluorescence and Optical Trapping Applied to Molecular Motors: Two can do it better than one.
Time: Mon 2012-12-10 15.15 - Mon 2014-01-13 16.00
Location: FB41
Kinesin and dynein are molecular motors that move
in opposite directions on a microtubule. They often act on the
same cargo, causing the cargo to frequently switch direction.
Whether this back-and-forth motion results from a coordinating
complex or from a tug-of-war between the two motors is currently
unknown. We have applied single molecule fluorescence to
determine that they are undergoing a synergistic tug-of-war. By
synergistic, we mean that the combination of the two motors is
able to bypass roadblocks along the microtubule. Furthermore,
using an in vivo optical trap, and by comparing directional stall
forces in vivo and in vitro, we found when cargo is going in the
positive microtubule direction, kinesin and dynein are pulling,
with the dynein walking backwards. The net stall force equals the
stall force of kinesin (≈ 7 pN) minus the stall forces of the
number of dyneins (1.1 pN x ND, where ND, = 0 to 6). When moving
in the negative microtubule direction, the stall force is just
equal to a multiple of dynein’s stall force (1.1 pN x ND),
implying that kinesin has fallen off the microtubule.