A new function for the gamma-tubulin ring complex as a microtubule minus-end cap.
Microtubule nucleation from centrosomes involves a lockwasher-shaped protein complex containing gamma-tubulin, named the gamma-tubulin ring complex (gammaTuRC). Here we investigate the mechanism by which the gammaTuRC nucleates microtubules, using a direct labelling method to visualize the behaviour of individual gammaTuRCs. A fluorescently-labelled version of the gammaTuRC binds to the minus ends of microtubules nucleated in vitro. Both gammaTuRC-mediated nucleation and binding of the gammaTuRC to preformed microtubules block further minus-end growth and prevent microtubule depolymerization. The gammaTuRC therefore acts as a minus-end-capping protein, as confirmed by electron-microscopic examination of gold-labelled gammaTuRCs. These data support a nucleation model for gammaTuRC function that involves capping of microtubules.
Wiese
C
C
Department of Embryology, Carnegie Institution of Washington, 115 West University Parkway, Baltimore, Maryland 21210, USA. wiese@ciwemb.edu
Zheng
Y
Y
D000818:Animals; D001704:Biopolymers / Q000737:chemistry / Q000378:metabolism; D001710:Biotin / Q000378:metabolism; D018385:Centrosome / Q000737:chemistry / Q000378:metabolism; D005452:Fluoresceins / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D006046:Gold; D008854:Microscopy, Electron; D008870:Microtubules / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008954:Models, Biological; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D014404:Tubulin / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D014982:Xenopus laevis
D001704:Biopolymers; D005452:Fluoresceins; D005456:Fluorescent Dyes; D014404:Tubulin; D001710:Biotin; D006046:Gold