GTP-Dependent Formation of Straight Oligomers Leads to Nucleation of Microtubules

Abstract

Microtubule (MT) nucleation is essential for cellular activities, but its mechanism is not known because of the difficulty involved in capturing rare stochastic events in the early stage of polymerization. in cells, MTs are nucleated at tubulin concentrations significantly lower than those required for spontaneous nucleation in vitro. The high efficiency of nucleation is due to the synergistic effects of various cellular factors, but the underlying mechanism has not been clarified yet. Here, combining negative stain electron microscopy and kinetic analysis, we demonstrate that the formation of single-stranded straight oligomers with critical size is essential for nucleation in vitro.