title: GTP regulates the microtubule nucleation activity of γ-tubulin.
abstract: Both subunits of αβ-tubulin that comprise the core components of microtubules bind GTP. GTP binding to α-tubulin has a structural role, whereas β-tubulin binds and hydrolyses GTP to regulate microtubule dynamics. γ-tubulin, another member of the tubulin superfamily that seeds microtubule nucleation at microtubule-organizing centres, also binds GTP; however, the importance of this association remains elusive. To address the role of GTP binding to γ-tubulin, we systematically mutagenized the GTP contact residues in the yeast γ-tubulin Tub4. Tub4(GTP)-mutant proteins that exhibited greatly reduced GTP affinity still assembled into the small γ-tubulin complex. However, tub4(GTP) mutants were no longer viable, and had defects in interaction between γ-tubulin and αβ-tubulin, decreased microtubule nucleation and defects in microtubule organization. In vitro and in vivo data show that only γ-tubulin loaded with GTP nucleates microtubules. Our results suggest that GTP recruitment to γ-tubulin enhances its interaction with αβ-tubulin similarly to GTP recruitment to β-tubulin.
authors.affiliation: Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), ZMBH-DKFZ Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany.
authors.forename: Linda
authors.initials: L
authors.lastname: Gombos
authors.forename: Annett
authors.initials: A
authors.lastname: Neuner
authors.forename: Mykhaylo
authors.initials: M
authors.lastname: Berynskyy
authors.forename: Luca L
authors.initials: LL
authors.lastname: Fava
authors.forename: Rebecca C
authors.initials: RC
authors.lastname: Wade
authors.forename: Carsten
authors.initials: C
authors.lastname: Sachse
authors.forename: Elmar
authors.initials: E
authors.lastname: Schiebel
mesh_terms: D006160:Guanosine Triphosphate / Q000502:physiology*; D008870:Microtubules / Q000502:physiology*; D008958:Models, Molecular; D012441:Saccharomyces cerevisiae / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology; D014404:Tubulin / Q000737:chemistry / Q000502:physiology*
chemical_list: D029701:Saccharomyces cerevisiae Proteins; D014404:Tubulin; D006160:Guanosine Triphosphate