Mechanism of how augmin directly targets the γ-tubulin ring complex to microtubules. Author Jae-Geun Song, Matthew King, Rui Zhang, Rachel Kadzik, Akanksha Thawani, Sabine Petry Publication Year 2018 Type Journal Article Abstract Microtubules (MTs) must be generated from precise locations to form the structural frameworks required for cell shape and function. MTs are nucleated by the γ-tubulin ring complex (γ-TuRC), but it remains unclear how γ-TuRC gets to the right location. Augmin has been suggested to be a γ-TuRC targeting factor and is required for MT nucleation from preexisting MTs. To determine augmin's architecture and function, we purified augmin from insect cells. We demonstrate that augmin is sufficient to target γ-TuRC to MTs by in vitro reconstitution. Augmin is composed of two functional parts. One module (tetramer-II) is necessary for MT binding, whereas the other (tetramer-III) interacts with γ-TuRC. Negative-stain electron microscopy reveals that both tetramers fit into the Y-shape of augmin, and MT branching assays reveal that both are necessary for MT nucleation. The finding that augmin can directly bridge MTs with γ-TuRC via these two tetramers adds to our mechanistic understanding of how MTs can be nucleated from preexisting MTs. Keywords Animals, Humans, Protein Binding, Protein Conformation, Microtubule-Associated Proteins, Cell Cycle Proteins, Xenopus laevis, Microtubules, Spindle Apparatus, Tubulin, Microtubule-Organizing Center Journal J Cell Biol Volume 217 Issue 7 Pages 2417-2428 Date Published 2018 Jul 02 ISSN Number 1540-8140 DOI 10.1083/jcb.201711090 Alternate Journal J Cell Biol PMCID PMC6028527 PMID 29875259 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML