title: Ring closure activates yeast γTuRC for species-specific microtubule nucleation.
abstract: The γ-tubulin ring complex (γTuRC) is the primary microtubule nucleator in cells. γTuRC is assembled from repeating γ-tubulin small complex (γTuSC) subunits and is thought to function as a template by presenting a γ-tubulin ring that mimics microtubule geometry. However, a previous yeast γTuRC structure showed γTuSC in an open conformation that prevents matching to microtubule symmetry. By contrast, we show here that γ-tubulin complexes are in a closed conformation when attached to microtubules. To confirm the functional importance of the closed γTuSC ring, we trapped the closed state and determined its structure, showing that the γ-tubulin ring precisely matches microtubule symmetry and providing detailed insight into γTuRC architecture. Importantly, the closed state is a stronger nucleator, thus suggesting that this conformational switch may allosterically control γTuRC activity. Finally, we demonstrate that γTuRCs have a strong preference for tubulin from the same species.
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, Washington, USA.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Kollman
authors.affiliation: 1] Department of Bioengineering and Therapeutic Sciences, University of California at San Francisco, San Francisco, California, USA. [2] Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, California, USA. [3] California Institute for Quantitative Biosciences (QB3), University of California at San Francisco, San Francisco, California, USA.
authors.forename: Charles H
authors.identifier: 0000000344128527
authors.initials: CH
authors.lastname: Greenberg
authors.affiliation: Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California, USA.
authors.forename: Sam
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Moritz
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, Washington, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Zelter
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, Washington, USA.
authors.forename: Kimberly K
authors.initials: KK
authors.lastname: Fong
authors.affiliation: Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Cientificas, Madrid, Spain.
authors.forename: Jose-Jesus
authors.initials: JJ
authors.lastname: Fernandez
authors.affiliation: 1] Department of Bioengineering and Therapeutic Sciences, University of California at San Francisco, San Francisco, California, USA. [2] Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, California, USA. [3] California Institute for Quantitative Biosciences (QB3), University of California at San Francisco, San Francisco, California, USA.
authors.forename: Andrej
authors.initials: A
authors.lastname: Sali
authors.affiliation: Medical Research Council Laboratory of Molecular Biology, Cambridge, UK.
authors.forename: John
authors.initials: J
authors.lastname: Kilmartin
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, Washington, USA.
authors.forename: Trisha N
authors.identifier: 0000000347973152
authors.initials: TN
authors.lastname: Davis
authors.affiliation: 1] Department of Biochemistry and Biophysics, University of California at San Francisco, San Francisco, California, USA. [2] Howard Hughes Medical Institute, University of California at San Francisco, San Francisco, California, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Agard
mesh_terms: D008870:Microtubules / Q000378:metabolism*; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism*; D014404:Tubulin / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D014404:Tubulin