Microtubule treadmilling

VII. Protomer Flux with Assembled Polymers (Microtubule Treadmilling ) 194... 

DYNAMIC INSTABILITY DEPOLYMERIZATION, END-WISE MICROTUBULE TREADMILLING POLYMERIZATION RANDOM SCISSION KINETICS DEPOLYMERIZATION, END-WISE Deracemization,... 

Microtubule depolymerization, DEPOLYMERIZATION, END-WISE MICROTUBULE TREADMILLING... 

Opposite-end assembly and disassembly, MICROTUBULE TREADMILLING MICROTUBULE ASSEMBLY KINETICS OPTICAL ACTIVITY OPTICAL DENSITY Optically active substance,... 

At steady state, a pool of free heterodimers (representing the critical concentration) coexists with filaments. For these filaments, the critical concentration is lower at the plus end than at the minus end. Thus, treadmilling can occur with a net loss of protomers from the minus end and net addition at the plus end. However, for microtubules, treadmilling is generally overshadowed by a related and much more dramatic phenomenon known as dynamic instability. If a filament loses its GTP cap at either end, depolymerization at that end occurs extremely rapidly. Thus, even at steady state, some filaments can be rapidly shortening at one or both ends while other filaments are rapidly growing at one or both ends. Dynamic instability also occurs in vivo and is an essential factor in the proper functioning of many microtubule-based networks. 

Margolis RL, Wilson L. Microtubule treadmilling What goes around comes around. Bioessays 1998 20 830-836. 

Though the above mechanism had value in describing the steady-state tubulin flux, Karr and Purich (1979) pointed out that a number of association-dissociation steps can occur for each net protomer addition. They found that the rate of isothermal dilution-induced disassembly of microtubules proceeded at rates 500- to 1000-fold greater than the observed treadmilling rate which itself corresponded to a turnover of about 7% of the tubulin pool/hour (Margolis and Wilson, 1978). Karr and Purich (1979) also proposed that the unidirectional treadmilling model be amended to account for the rapidity of on-off events at the polymer ends, and they offered the alternative mechanism presented here. 

ACTIN ASSEMBLY KINETICS ACTIN-BASED MOTILITY MICROTUBULE ASSEMBLY KINETICS TREADMILLING... 

The spindle contains a number of dynein- and kinesin-family motors (Fig. 5-37). These, together with the dynamic instability and treadmilling of the microtubules, help control the movement and relative positions of the chromosomes and the poles. The spindle is under constant tension resulting from a range of forces. 

Panda D, Miller HP, Wilson L. Rapid treadmilling of brain microtubules free of microtubule-associated proteins in vitro and its suppression by tan. Proc. Natl. Acad. Sci. U.S.A. 1999 96 12459-12464. 

Manna T, Thrower D, Miller HP, Curmi P, Wilson L. Stathmin strongly increases the minus end catastrophe frequency and induces rapid treadmilling of bovine brain microtubules at steady state in vitro. J. Biol. Chem. 2006 281 2071-2078. 

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