Institute of Structural and Molecular Biology, Crystallography, Department of Biological Sciences, Birkbeck College, University of London, London, UK. reda.rawi@uni-due.de|Institute of Structural and Molecular Biology, Crystallography, Department of Biological Sciences, Birkbeck College, University of London, London, UK. reda.rawi@uni-due.de|Institute of Structural and Molecular Biology, Crystallography, Department of Biological Sciences, Birkbeck College, University of London, London, UK. reda.rawi@uni-due.de