Discovery of Cs selective binding site on a halophilic protein

Arai, Shigeki; Adachi, Motoyasu; Tamada, Taro; Tokunaga, Hiroko*; Ishibashi, Matsujiro*; Tokunaga, Masao*; Kuroki, Ryota

no journal, , 

Because various metal ion binding sites exist on halophilic proteins, we proposed that the metal ion binding sites with an affinity to harmful metals and rare metals could be identified using X-ray crystallographic analysis in the presence of those metal ions. In this study, we attempted to identify metal ion binding sites for Sr and Cs on a halophilic protein HaBLA derived from sp.560 (HaBLA) by X-ray crystallographic analysis and anomalous X-ray diffraction analysis. By these analyses, we succeeded in discovering one Cs binding site and three Sr binding site for one molecule of HaBLA. Moreover, discovered Cs binding site showed high Cs selectivity, which binds Cs even in the presence of 9-fold molar excess of Na (90 mM Na / 10 mM Cs).