J. Biol. Chem., Vol. 255, Issue 18, 8560-8566, Sep, 1980
Mechanism of microtubule depolymerization. Correlation of rapid induced disassembly experiments with a kinetic model for endwise depolymerization
TL Karr, D Kristofferson and DL Purich
Microtubule disassembly has been studied using a rapid dilution technique
(Karr, T.L., and Purich, D.L. (1979) J. Biol. Chem. 254, 10885-10888).
Disassembly curves, generated by computer from the solution of series first
order differential equations (see following paper), were fit to
experimental data with excellent agreement when the diluted microtubules
contained no microtubule-associated proteins. The rate constant for dimer
release from microtubules was found to be 154 s- 1. Assuming a critical
tubulin concentration of 8 to 9 x 10(-6) M, the apparent bimolecular rate
constant (2 x 10(7) M-1 s-1) for assembly is near the diffusion limit. It
was also possible to use the rapid dilution technique for quantitatively
correlating the disassembly rate to the number concentration of microtubule
ends. These findings suggest that the dynamics of tubulin interactions with
microtubules may be characterized in terms of an endwise depolymerization
model. A re- evaluation of cold induced depolymerization kinetics (see
miniprint supplement) is also fully consistent with our analysis of
disassembly dynamics.
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