title: IM30 triggers membrane fusion in cyanobacteria and chloroplasts.
abstract: The thylakoid membrane of chloroplasts and cyanobacteria is a unique internal membrane system harbouring the complexes of the photosynthetic electron transfer chain. Despite their apparent importance, little is known about the biogenesis and maintenance of thylakoid membranes. Although membrane fusion events are essential for the formation of thylakoid membranes, proteins involved in membrane fusion have yet to be identified in photosynthetic cells or organelles. Here we show that IM30, a conserved chloroplast and cyanobacterial protein of approximately 30 kDa binds as an oligomeric ring in a well-defined geometry specifically to membranes containing anionic lipids. Triggered by Mg(2+), membrane binding causes destabilization and eventually results in membrane fusion. We propose that IM30 establishes contacts between internal membrane sites and promotes fusion to enable regulated exchange of proteins and/or lipids in cyanobacteria and chloroplasts.
authors.affiliation: Institut für Pharmazie and Biochemie, Johannes Gutenberg-Universität Mainz, Johann-Joachim-Becher-Weg 30, 55128 Mainz, Germany.
authors.forename: Raoul
authors.initials: R
authors.lastname: Hennig
authors.affiliation: Institut für Pharmazie and Biochemie, Johannes Gutenberg-Universität Mainz, Johann-Joachim-Becher-Weg 30, 55128 Mainz, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Heidrich
authors.affiliation: Institut für Zoologie, Johannes Gutenberg-Universität Mainz, Johannes-von-Müller-Weg 6, 55128 Mainz, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Saur
authors.affiliation: Max Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Schmüser
authors.affiliation: Vant Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Roeters
authors.affiliation: Institut für Molekulare Biophysik, Johannes Gutenberg-Universität Mainz, Jakob-Welder-Weg 26, 55128, Mainz, Germany.
authors.forename: Nadja
authors.initials: N
authors.lastname: Hellmann
authors.affiliation: Vant Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
authors.forename: Sander
authors.initials: S
authors.lastname: Woutersen
authors.affiliation: Max Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Mischa
authors.initials: M
authors.lastname: Bonn
authors.affiliation: 1] Max Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany [2] Department of Chemical Engineering, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Tobias
authors.initials: T
authors.lastname: Weidner
authors.affiliation: Institut für Zoologie, Johannes Gutenberg-Universität Mainz, Johannes-von-Müller-Weg 6, 55128 Mainz, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Markl
authors.affiliation: Institut für Pharmazie and Biochemie, Johannes Gutenberg-Universität Mainz, Johann-Joachim-Becher-Weg 30, 55128 Mainz, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Schneider
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism* / Q000648:ultrastructure; D002499:Centrifugation, Density Gradient; D002736:Chloroplasts / Q000378:metabolism*; D038983:Galactolipids / Q000378:metabolism; D006017:Glycolipids / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism; D008561:Membrane Fusion; D010715:Phosphatidylglycerols / Q000378:metabolism; D011485:Protein Binding; D046939:Synechocystis / Q000378:metabolism*; D020524:Thylakoids
chemical_list: D001426:Bacterial Proteins; D038983:Galactolipids; D006017:Glycolipids; D008081:Liposomes; D010715:Phosphatidylglycerols; C009909:monogalactosyldiacylglycerol; C013694:sulfoquinovosyl diglyceride