Microtubule Depolymerization by the Kinesin-8 Motor Kip3p: A Mathematical Model |
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Authors: | LE Hough Matthew A Glaser MD Betterton |
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Institution: | † Physics Department, University of Colorado at Boulder, Boulder, Colorado ‡ Chemistry and Biochemistry Department, University of Colorado at Boulder, Boulder, Colorado § Molecular, Cell, and Developmental Biology Department, University of Colorado at Boulder, Boulder, Colorado |
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Abstract: | Proteins from the kinesin-8 family promote microtubule (MT) depolymerization, a process thought to be important for the control of microtubule length in living cells. In addition to this MT shortening activity, kinesin 8s are motors that show plus-end directed motility on MTs. Here we describe a simple model that incorporates directional motion and destabilization of the MT plus-end by kinesin 8. Our model quantitatively reproduces the key features of length-versus-time traces for stabilized MTs in the presence of purified kinesin 8, including length-dependent depolymerization. Comparison of model predictions with experiments suggests that kinesin 8 depolymerizes processively, i.e., one motor can remove multiple tubulin dimers from a stabilized MT. Fluctuations in MT length as a function of time are related to depolymerization processivity. We have also determined the parameter regime in which the rate of MT depolymerization is length dependent: length-dependent depolymerization occurs only when MTs are sufficiently short; this crossover is sensitive to the bulk motor concentration. |
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