1. Institute of Molecular Biosciences and ‘Cluster of Excellence Macromolecular Complexes’, Department of Biosciences, J.W. Goethe-University, Max-von-Laue-Str. 9, D-60438 Frankfurt am Main, Germany
2. Protein Research Group, Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campus 55, DK-5230 Odense M, Denmark