Division of Structural Biology, German Research Centre for Biotechnology (GBF) Mascheroder Weg 1, D-38124, Braunschweig, Germany. Reichelt@gbf.de|Division of Structural Biology, German Research Centre for Biotechnology (GBF) Mascheroder Weg 1, D-38124, Braunschweig, Germany. Reichelt@gbf.de|Division of Structural Biology, German Research Centre for Biotechnology (GBF) Mascheroder Weg 1, D-38124, Braunschweig, Germany. Reichelt@gbf.de|Division of Structural Biology, German Research Centre for Biotechnology (GBF) Mascheroder Weg 1, D-38124, Braunschweig, Germany. Reichelt@gbf.de|Division of Structural Biology, German Research Centre for Biotechnology (GBF) Mascheroder Weg 1, D-38124, Braunschweig, Germany. Reichelt@gbf.de