FIGURE 18-7 The γ-tubulin ring complex (γ-TuRC) that nucleates microtubule assembly. (a) Immunofluorescence micrograph in which microtubules assembled in vitro are labeled green and a component of the γ-TuRC is labeled red, showing that it is located specifically at one end of the microtubule. (b) Model of how γ-TuRC nucleates assembly of a microtubule by forming a template corresponding to the (−) end.

[Part (a) reprinted by permission from Macmillan Publishers Ltd: Keating, T.J. and Borisy, G.G., “Immunostructural evidence for the template mechanism of microtubule nucleation,” Nature Cell Biology, 2:352, copyright 2000.]