The kinetics of microtubule assembly. Evidence for a two-stage nucleation mechanism.

摘要: A model describing the nucleation and assembly of purified tubulin has been developed. The novel feature this is a two stage process to allow explicit inclusion two-dimensional nature early stages microtubule assembly. In actin small starting nucleus only one site for subunit addition as two-stranded helix formed. contrast, begins with formation section wall. we propose modification work Wegner Engel (Wegner, A., Engel, J. (1975) Biophys. Chem. 3, 215-225) wherein add second directly account lateral growth, i.e. number subunits side an existing sheet structure. Subsequent elongation sheets treated in usual way. experimental system used test was Mg2+/glycerol induced tubulin. computer simulation polymerization time courses gave fairly good fit kinetics our model, where primary comprises protofilaments, four three subunits, growth requires three-subunit initiate new protofilament.