Monitoring Editor: Tim Stearns The gamma-tubulin small complex (gamma-TuSC) is an evolutionarily conserved heterotetramer essential for microtubule nucleation. We have determined the structure of the S. cerevisiae gamma-TuSC at 25 A resolution by electron microscopy. gamma-TuSC is Y-shaped, with an elongated body connected to two arms. Gold labeling showed that the two gamma-tubulins are located in lobes at the ends of the arms, and the relative orientations of the other gamma-TuSC components were determined by in vivo FRET. The structures of different subpopulations of gamma-TuSC indicate flexibility in the connection between a mobile arm and the rest of the complex, resulting in variation of the relative positions and orientations of the gamma-tubulins. In all of the structures the gamma-tubulins are distinctly separated, a configuration incompatible with the microtubule lattice. The separation of the gamma-tubulins in isolated gamma-TuSC likely plays a role in suppressing its intrinsic microtubule nucleating activity, which is relatively weak until the gamma-TuSC is incorporated into higher-order complexes or localized to microtubule organizing centers. We propose that further movement of the mobile arm is required to bring the gamma-tubulins together in microtubule-like interactions, and provide a template for microtubule growth.
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|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|