title: Nucleotides and substrates trigger the dynamics of the Toc34 GTPase homodimer involved in chloroplast preprotein translocation.
abstract: GTPases are molecular switches that control numerous crucial cellular processes. Unlike bona fide GTPases, which are regulated by intramolecular structural transitions, the less well studied GAD-GTPases are activated by nucleotide-dependent dimerization. A member of this family is the translocase of the outer envelope membrane of chloroplast Toc34 involved in regulation of preprotein import. The GTPase cycle of Toc34 is considered a major circuit of translocation regulation. Contrary to expectations, previous studies yielded only marginal structural changes of dimeric Toc34 in response to different nucleotide loads. Referencing PELDOR and FRET single-molecule and bulk experiments, we describe a nucleotide-dependent transition of the dimer flexibility from a tight GDP- to a flexible GTP-loaded state. Substrate binding induces an opening of the GDP-loaded dimer. Thus, the structural dynamics of bona fide GTPases induced by GTP hydrolysis is replaced by substrate-dependent dimer flexibility, which likely represents a general regulatory mode for dimerizing GTPases.
authors.affiliation: Physics Department E22 and IMETUM, Technical University Munich, 85748 Garching, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Lumme
authors.affiliation: Institute of Molecular Cell Biology of Plants, Goethe University, 60438 Frankfurt, Germany.
authors.forename: Hasret
authors.initials: H
authors.lastname: Altan-Martin
authors.affiliation: Institute of Physical and Theoretical Chemistry, Goethe University, 60438 Frankfurt, Germany; Cluster of Excellence "Macromolecular Complexes", Goethe University, 60438 Frankfurt, Germany; Center for Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt, Germany; Department of Molecular Physiology & Biophysics, Vanderbilt University, 741 Light Hall, 2215 Garland Avenue, Nashville, TN 37232, USA.
authors.forename: Reza
authors.initials: R
authors.lastname: Dastvan
authors.affiliation: Institute of Molecular Cell Biology of Plants, Goethe University, 60438 Frankfurt, Germany.
authors.forename: Maik S
authors.initials: MS
authors.lastname: Sommer
authors.affiliation: Physics Department E22 and IMETUM, Technical University Munich, 85748 Garching, Germany.
authors.forename: Mislav
authors.initials: M
authors.lastname: Oreb
authors.affiliation: Institute of Physical and Theoretical Chemistry, Goethe University, 60438 Frankfurt, Germany; Cluster of Excellence "Macromolecular Complexes", Goethe University, 60438 Frankfurt, Germany; Center for Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt, Germany.
authors.forename: Denise
authors.initials: D
authors.lastname: Schuetz
authors.affiliation: Physics Department E22 and IMETUM, Technical University Munich, 85748 Garching, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Hellenkamp
authors.affiliation: Institute of Molecular Cell Biology of Plants, Goethe University, 60438 Frankfurt, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Mirus
authors.affiliation: Institute of Molecular Cell Biology of Plants, Goethe University, 60438 Frankfurt, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Kretschmer
authors.affiliation: Institute of Physical and Theoretical Chemistry, Goethe University, 60438 Frankfurt, Germany; Cluster of Excellence "Macromolecular Complexes", Goethe University, 60438 Frankfurt, Germany; Center for Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt, Germany.
authors.forename: Sevdalina
authors.initials: S
authors.lastname: Lyubenova
authors.affiliation: Physics Department, Ulm University, 89081 Ulm, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kügel
authors.affiliation: Institute of Molecular Cell Biology of Plants, Goethe University, 60438 Frankfurt, Germany.
authors.forename: Jan P
authors.initials: JP
authors.lastname: Medelnik
authors.affiliation: Institute of Molecular Cell Biology of Plants, Goethe University, 60438 Frankfurt, Germany.
authors.forename: Manuela
authors.initials: M
authors.lastname: Dehmer
authors.affiliation: Physics Department, Ulm University, 89081 Ulm, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Michaelis
authors.affiliation: Institute of Physical and Theoretical Chemistry, Goethe University, 60438 Frankfurt, Germany; Cluster of Excellence "Macromolecular Complexes", Goethe University, 60438 Frankfurt, Germany; Center for Biomolecular Magnetic Resonance, Goethe University, 60438 Frankfurt, Germany.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Prisner
authors.affiliation: Physics Department E22 and IMETUM, Technical University Munich, 85748 Garching, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Hugel
authors.affiliation: Institute of Molecular Cell Biology of Plants, Goethe University, 60438 Frankfurt, Germany; Cluster of Excellence "Macromolecular Complexes", Goethe University, 60438 Frankfurt, Germany; Center for Membrane Proteomics, Goethe University, 60438 Frankfurt, Germany. Electronic address: schleiff@bio.uni-frankfurt.de.
authors.forename: Enrico
authors.initials: E
authors.lastname: Schleiff
mesh_terms: D000595:Amino Acid Sequence; D002736:Chloroplasts / Q000737:chemistry*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006153:Guanosine Diphosphate / Q000737:chemistry*; D006160:Guanosine Triphosphate / Q000737:chemistry*; D007700:Kinetics; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018532:Pisum sativum / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics; D011485:Protein Binding; D055503:Protein Multimerization; D011498:Protein Precursors / Q000737:chemistry* / Q000235:genetics; D021381:Protein Transport; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D013379:Substrate Specificity; D013816:Thermodynamics
chemical_list: D008565:Membrane Proteins; D010940:Plant Proteins; D011498:Protein Precursors; D011994:Recombinant Proteins; C112475:Toc34 protein, plant; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate