  The coupling between the depolymerization of microtubules (MTs) and the
motion of the Dam1 ring complex is now thought to play an important role in the
generation of forces during mitosis. Our current understanding of this motion
is based on a number of detailed computational models. Although these models
realize possible mechanisms for force transduction, they can be extended by
variation of any of a large number of poorly measured parameters and there is
no clear strategy for determining how they might be distinguished
experimentally. Here we seek to identify and analyze two distinct mechanisms
present in the computational models. In the first the splayed protofilaments at
the end of the depolymerizing MT physically prevent the Dam1 ring from falling
off the end, in the other an attractive binding secures the ring to the
microtubule. Based on this analysis, we discuss how to distinguish between
competing models that seek to explain how the Dam1 ring stays on the MT. We
propose novel experimental approaches that could resolve these models for the
first time, either by changing the diffusion constant of the Dam1 ring (e.g.,
by tethering a long polymer to it) or by using a time varying load.
