IM30 triggers membrane fusion in cyanobacteria and chloroplasts

• Published in: Nature communications Vol. 6; no. 1; p. 7018
• Main Authors: Hennig, Raoul, Heidrich, Jennifer, Saur, Michael, Schmüser, Lars, Roeters, Steven J., Hellmann, Nadja, Woutersen, Sander, Bonn, Mischa, Weidner, Tobias, Markl, Jürgen, Schneider, Dirk
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 08.05.2015; Nature Publishing Group
• Subjects: 631/449/1734; 631/449/448/1374; 631/80/313/2378; 82/80; Bacterial Proteins - metabolism; Bacterial Proteins - ultrastructure; Centrifugation, Density Gradient; Chloroplasts - metabolism; Galactolipids - metabolism; Glycolipids - metabolism; Humanities and Social Sciences; Liposomes - metabolism; Membrane Fusion; multidisciplinary; Phosphatidylglycerols - metabolism; Protein Binding; Science; Science (multidisciplinary); Synechocystis - metabolism; Thylakoids
• ISSN: 2041-1723
• DOI: 10.1038/ncomms8018

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. Thylakoid membranes are critical components of chloroplasts and cyanobacteria. Here, Hennig et al . demonstrate that IM30, a conserved chloroplast and cyanobacterial protein, binds to thylakoid membranes and can trigger membrane destabilization and fusion in a Mg2 + dependent manner.