Overall structure of EF-EG2. Inner and outer helices of the (α/α)6 barrel, other short helices and β-strands are colored in cyan, blue, light purple and magenta, respectively. Crystallization reagents and putative active residues are shown as purple and magenta stick models, respectively. Two ions, calcium and sodium, are shown as green and purple sphere models, respectively. All figures were prepared using the PyMOL Molecular Graphics System (DeLano Scientific, San Carlos, CA, USA).