Protein Structure Factory, Max Planck Institute of Molecular Genetics, Heubnerweg 6, 14059 Berlin, Germany. buessow@molgen.mpg.de|Protein Structure Factory, Max Planck Institute of Molecular Genetics, Heubnerweg 6, 14059 Berlin, Germany. buessow@molgen.mpg.de|Protein Structure Factory, Max Planck Institute of Molecular Genetics, Heubnerweg 6, 14059 Berlin, Germany. buessow@molgen.mpg.de