Structure of the gamma-tubulin ring complex: a template for microtubule nucleation.
The gamma-tubulin ring complex (gammaTuRC) is a protein complex of relative molecular mass approximately 2.2 x 10(6) that nucleates microtubules at the centrosome. Here we use electron-microscopic tomography and metal shadowing to examine the structure of isolated Drosophila gammaTuRCs and the ends of microtubules nucleated by gammaTuRCs and by centrosomes. We show that the gammaTuRC is a lockwasher-like structure made up of repeating subunits, topped asymmetrically with a cap. A similar capped ring is also visible at one end of microtubules grown from isolated gammaTuRCs and from centrosomes. Antibodies against gamma-tubulin label microtubule ends, but not walls, in centrosomes. These data are consistent with a template-mediated mechanism for microtubule nucleation by the gammaTuRC.
Moritz
M
M
Department of Biochemistry and Biophysics, Howard Hughes Medical Institute, University of California, 513 Parnassus Avenue, San Francisco, California 94143, USA. moritz@msg.ucsf.edu
Braunfeld
M B
MB
Guénebaut
V
V
Heuser
J
J
Agard
D A
DA
D000818:Animals; D000906:Antibodies / Q000276:immunology; D001704:Biopolymers / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D018385:Centrosome / Q000737:chemistry / Q000276:immunology / Q000378:metabolism / Q000648:ultrastructure; D004331:Drosophila melanogaster; D008854:Microscopy, Electron; D008870:Microtubules / Q000737:chemistry / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure*; D008954:Models, Biological; D008970:Molecular Weight; D010984:Platinum; D011233:Precipitin Tests; D020836:Protein Structure, Quaternary; D016628:Replica Techniques; D016626:Shadowing Technique, Histology; D014404:Tubulin / Q000737:chemistry / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure*
D000906:Antibodies; D001704:Biopolymers; D014404:Tubulin; D010984:Platinum