5fm1 | pdb_00005fm1
Structure of gamma-tubulin small complex based on a cryo-EM map, chemical cross-links, and a remotely related structure
Structural highlights
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Function[SPC97_YEAST] Involved in microtubule organization by the microtubule organizing center, the spindle pole body (SPB). Probably part of the microtubule attachment site at the SPB. [TBG_YEAST] Tubulin is the major constituent of microtubules. The gamma chain is found at microtubule organizing centers (MTOC) such as the spindle poles or the centrosome, suggesting that it is involved in the minus-end nucleation of microtubule assembly. TUB4 is an important spindle pole body component that organizes both cytoplasmic and nuclear microtubule arrays. [SPC98_YEAST] Involved in microtubule organization by the microtubule organizing center, the spindle pole body (SPB). Probably part of the microtubule attachment site at the SPB. Publication Abstract from PubMedMicrotubules 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. 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[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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