1. Karolinska Institutet NOVUM, Center for Structural Biochemistry, S-14157 Huddinge, Sweden, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE−171 77 Stockholm, Sweden, Global Phasing Ltd. Sheraton House, Castle Park, Cambridge CB30AX, UK, and Faculty of Natural Sciences, Södertörn University College, SE−141 04 Huddinge, Sweden