gamma-Tubulin complexes are essential for microtubule (MT) nucleation. The gamma-tubulin small complex (gamma-TuSC) consists of two molecules of gamma-tubulin and one molecule each of Spc97 and Spc98. In vitro, gamma-TuSCs oligomerize into spirals of 13 gamma-tubulin molecules per turn. However, the properties and numbers of gamma-TuSCs at MT nucleation sites in vivo are unclear. In this paper, we show by fluorescence recovery after photobleaching analysis that gamma-tubulin was stably integrated into MT nucleation sites and was further stabilized by tubulin binding. Importantly, tubulin showed a stronger interaction with the nucleation site than with the MT plus end, which probably provides the basis for MT nucleation. Quantitative analysis of gamma-TuSCs on single MT minus ends argued for nucleation sites consisting of approximately seven gamma-TuSCs with approximately three additional gamma-tubulin molecules. Nucleation and anchoring of MTs required the same number of gamma-tubulin molecules. We suggest that a spiral of seven gamma-TuSCs with a slight surplus of gamma-tubulin nucleates MTs in vivo.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Annotation Extension||Reference|
|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||Assay||Construct||Conditions||Strain Background||Reference|