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5fm1

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{{Large structure}}
==Structure of gamma-tubulin small complex based on a cryo-EM map, chemical cross-links, and a remotely related structure==
==Structure of gamma-tubulin small complex based on a cryo-EM map, chemical cross-links, and a remotely related structure==
<StructureSection load='5fm1' size='340' side='right' caption='[[5fm1]], [[Resolution|resolution]] 8.00&Aring;' scene=''>
<StructureSection load='5fm1' size='340' side='right' caption='[[5fm1]], [[Resolution|resolution]] 8.00&Aring;' scene=''>
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<div style="background-color:#fffaf0;">
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
== Publication Abstract from PubMed ==
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Microtubules are nucleated in vivo by gamma-tubulin complexes. The 300-kDa gamma-tubulin small complex (gamma-TuSC), consisting of two molecules of gamma-tubulin and one copy each of the accessory proteins Spc97 and Spc98, is the conserved, essential core of the microtubule nucleating machinery. In metazoa multiple gamma-TuSCs assemble with other proteins into gamma-tubulin ring complexes (gamma-TuRCs). The structure of gamma-TuRC indicated that it functions as a microtubule template. Because each gamma-TuSC contains two molecules of gamma-tubulin, it was assumed that the gamma-TuRC-specific proteins are required to organize gamma-TuSCs to match 13-fold microtubule symmetry. Here we show that Saccharomyces cerevisiae gamma-TuSC forms rings even in the absence of other gamma-TuRC components. The yeast adaptor protein Spc110 stabilizes the rings into extended filaments and is required for oligomer formation under physiological buffer conditions. The 8-A cryo-electron microscopic reconstruction of the filament reveals 13 gamma-tubulins per turn, matching microtubule symmetry, with plus ends exposed for interaction with microtubules, implying that one turn of the filament constitutes a microtubule template. The domain structures of Spc97 and Spc98 suggest functions for conserved sequence motifs, with implications for the gamma-TuRC-specific proteins. The gamma-TuSC filaments nucleate microtubules at a low level, and the structure provides a strong hypothesis for how nucleation is regulated, converting this less active form to a potent nucleator.
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Modeling protein complex structures based on distantly related homologues can be challenging due to poor sequence and structure conservation. Therefore, utilizing even low-resolution experimental data can significantly increase model precision and accuracy. Here, we present models of the two key functional states of the yeast gamma-tubulin small complex (gammaTuSC): one for the low-activity "open" state and another for the higher-activity "closed" state. Both models were computed based on remotely related template structures and cryo-EM density maps at 6.9A and 8.0A resolution, respectively. For each state, extensive sampling of alignments and conformations was guided by the fit to the corresponding cryo-EM density map. The resulting good-scoring models formed a tightly clustered ensemble of conformations in most regions. We found significant structural differences between the two states, primarily in the gamma-tubulin subunit regions where the microtubule binds. We also report a set of chemical cross-links that were found to be consistent with equilibrium between the open and closed states. The protocols developed here have been incorporated into our open-source Integrative Modeling Platform (IMP) software package (http://integrativemodeling.org), and can therefore be applied to many other systems.
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Microtubule nucleating gamma-TuSC assembles structures with 13-fold microtubule-like symmetry.,Kollman JM, Polka JK, Zelter A, Davis TN, Agard DA Nature. 2010 Aug 12;466(7308):879-82. doi: 10.1038/nature09207. Epub 2010 Jul 14. PMID:20631709<ref>PMID:20631709</ref>
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Structure of gamma-tubulin small complex based on a cryo-EM map, chemical cross-links, and a remotely related structure.,Greenberg CH, Kollman J, Zelter A, Johnson R, MacCoss MJ, Davis TN, Agard DA, Sali A J Struct Biol. 2016 Jun;194(3):303-10. doi: 10.1016/j.jsb.2016.03.006. Epub 2016 , Mar 8. PMID:26968363<ref>PMID:26968363</ref>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

Revision as of 17:02, 10 May 2016

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Structure of gamma-tubulin small complex based on a cryo-EM map, chemical cross-links, and a remotely related structure

5fm1, resolution 8.00Å

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