title: A ternary membrane protein complex anchors the spindle pole body in the nuclear envelope in budding yeast.
abstract: In budding yeast (Saccharomyces cerevisiae) the multilayered spindle pole body (SPB) is embedded in the nuclear envelope (NE) at fusion sites of the inner and outer nuclear membrane. The SPB is built from 18 different proteins, including the three integral membrane proteins Mps3, Ndc1, and Mps2. These membrane proteins play an essential role in the insertion of the new SPB into the NE. How the huge core structure of the SPB is anchored in the NE has not been investigated thoroughly until now. The present model suggests that the NE protein Mps2 interacts via Bbp1 with Spc29, one of the coiled-coil proteins forming the central plaque of the SPB. To test this model, we purified and reconstituted the Mps2-Bbp1 complex from yeast and incorporated the complex into liposomes. We also demonstrated that Mps2-Bbp1 directly interacts with Mps3 and Ndc1. We then purified Spc29 and reconstituted the ternary Mps2-Bbp1-Spc29 complex, proving that Bbp1 can simultaneously interact with Mps2 and Spc29 and in this way link the central plaque of the SPB to the nuclear envelope. Interestingly, Bbp1 induced oligomerization of Spc29, which may represent an early step in SPB duplication. Together, this analysis provides important insights into the interaction network that inserts the new SPB into the NE and indicates that the Mps2-Bbp1 complex is the central unit of the SPB membrane anchor.
authors.affiliation: Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kupke
authors.affiliation: Biochemie-Zentrum der Universität Heidelberg (BZH), Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Malsam
authors.affiliation: Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Allianz, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany. Electronic address: e.schiebel@zmbh.uni-heidelberg.de.
authors.forename: Elmar
authors.initials: E
authors.lastname: Schiebel
mesh_terms: D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008868:Microtubule Proteins / Q000235:genetics / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009685:Nuclear Envelope / Q000235:genetics / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D064048:Spindle Pole Bodies / Q000235:genetics / Q000378:metabolism*
chemical_list: C404863:BBP1 protein, S cerevisiae; C120755:MPS2 protein, S cerevisiae; D008565:Membrane Proteins; D008868:Microtubule Proteins; D008869:Microtubule-Associated Proteins; C471174:Mps3 protein, S cerevisiae; D046912:Multiprotein Complexes; C082594:NDC1 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; C505600:Spc29 protein, S cerevisiae
keywords: Saccharomyces cerevisiae; cell biology; membrane protein; molecular cell biology; recombinant protein expression