Orientation-Selective Incorporation of Transmembrane F 0 F 1 ATP Synthase Complex from Micrococcus luteus in Polymer-Supported Membranes Murat Tutus, Fernanda F. Rossetti, Emanuel Schneck, Giovanna Fragneto, Friedrich Fo ¨rster, Ralf Richter, Thomas Nawroth, Motomu Tanaka * Introduction Biological membranes are vital components that define the outer boundary of living cells and organelles. They consist largely of a lipid bilayer and membrane-associated proteins that facilitate specific recognition on the mem- brane and material transport across the membrane. To bypass the structural complexity of biological membranes and their dynamic interactions with intra- and extra- cellular networks, artificial model membranes have played an important role in unraveling the physical and chemical characteristics of membranes and the resulting biological functions. Among various model membranes, phospholi- pid bilayers deposited onto solid substrates (so-called solid supported membranes) have been the most widely used Full Paper M. Tutus, F. F. Rossetti, E. Schneck, R. Richter, M. Tanaka Biophysical Chemistry Laboratory and Center for Quantitative Biology (BIOQUANT), University of Heidelberg, 69120 Heidelberg, Germany E-mail: tanaka@uni-heidelberg.de M. Tutus, F. F. Rossetti, E. Schneck, T. Nawroth, M. Tanaka Department of Physics, Technical University of Munich, D85748 Garching, Germany G. Fragneto Institut Laue-Langevin, F38043 Grenoble Cedex, France F.Fo¨rster Department of Molecular Structural Biology, Max Planck Institute for Biochemistry, 82152 Martinsried, Germany R. Richter Current address: Biosurfaces Unit, CIC biomaGUNE, 20009 San Sebastian, Spain T. Nawroth Current address: Institute of Pharmacy, University of Mainz, Staudingerweg 5, 55099 Mainz, Germany We report the vectorial incorporation of a highly asymmetric F 0 F 1 ATP synthase complex from Micrococcus luteus into polymer-supported membranes. Dynamic light scattering and cryo electron microscopy confirm that the use of weak surfactants (bile acid) allows for the non- disruptive protein incorporation into lipid vesicles. Spreading of vesicles with ATP synthase onto a cellulose support results in a homogeneous distribution of proteins, in contrast to a patchy image observed on bare glass slides. The orien- tation of ATP synthase can be identified using an antibody to the ATP binding site as well as from topographic profiles of the surface. The method to ‘‘align’’ transmembrane proteins in supported membranes would open a possibility to quantify protein functions in biomimetic model systems. 1034 Macromol. Biosci. 2008, 8, 1034–1043 ß 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/mabi.200800128