Figure 3
Presence of metal ions in the CHAP K crystal structure. A. X-ray fluorescence emission spectrum collected from a CHAPK crystal irradiated with monochromatic synchrotron radiation (12.7 KeV). B. Detail of the calcium ion coordination. Coordinating atoms are one Oδ atom of each of Asp45 and Asp47 residues, both Oδ atoms of Asp56, the main chain oxygen atoms of Tyr49 and His51 and an ordered water molecule (behind the calcium ion in this view). C. Detail of the zinc coordination. The zinc ion is sandwiched between Cys54 and the sulphate group of the MES ion, about 10 Å away from the calcium ion.