1. Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Flemingovo nám 2, 166 10 Prague 6, Czech Republic
2. Institute of Molecular Genetics, The Czech Academy of Sciences, Flemingovo n. 2, 166 37 Prague 6, Czech Republic
3. York Structural Biology Laboratory, Department of Chemistry, The University of York, Heslington, York YO10 5DD, United Kingdom