1. Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9712 CP Groningen, The Netherlands
2. Zernike Institute for Advanced Materials, University of Groningen, 9712 CP Groningen, The Netherlands
3. Molecular Microbiology and Structural Biochemistry (MMSB, UMR 5086), CNRS, University of Lyon, 69367 Lyon Cedex 07, France