Engineering Approaches to Biomolecular Motors

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Engineering Approaches to Biomolecular Motors: From in vitro to in vivo Poster Abstracts
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Understanding the Role of ATP in Active Self-organization of Microtubule Spools
Amanda J. Tan1, Dail E. Chapman2, Linda S. Hirst1, Jing Xu1.
1University of California, Merced, CA, USA, 2University of California, Irvine, CA, USA.
Self-organization of microtubules into ring-shaped structures (“spools”) constitutes a model
system for studying active material. To form microtubule spools, biotinylated microtubules are
shuttled atop a motor-coated surface as in standard gliding assays; binding between microtubules
is mediated by streptavidin. While the mechanisms underlying microtubule spool formation
remain unclear, it is known that considerable energy (105 kBT) is required to deform
microtubules to form spools. Here, we investigated the role of kinetic energy input (ATP) in
microtubule spool formation. We systematically varied the ATP concentration in our
experiments and examined the steady state size and number density of microtubule spools
formed under otherwise identical conditions. Surprisingly, we found that although ATP is
necessary to initiate spool formation and to sustain spool rotation, the steady state of microtubule
self-organization is not sensitive to ATP concentration. We detected no significant changes in the
morphology (spool circumference) or the probability of microtubule spools formed (number
density) over a 20-fold range in ATP concentration (0.05 – 1 mM). Our study indicates that
microtubule spool formation is not directly coupled to any particular level of kinetic energy
input. Lowering the ATP concentration, which slows the kinetic rate of microtubule self-
organization, may therefore be a useful experimental approach for understanding the
mechanisms underlying microtubule spool formation.