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Structure of a highly acidic $$beta$$-lactamase from the moderate halophile ${it Chromohalobacter}$ sp.560 and the discovery of a Cs$$^{+}$$-selective binding site

Arai, Shigeki; Yonezawa, Yasushi*; Okazaki, Nobuo*; Matsumoto, Fumiko*; Shibazaki, Chie; Shimizu, Rumi; Yamada, Mitsugu*; Adachi, Motoyasu; Tamada, Taro; Kawamoto, Masahide*; Tokunaga, Hiroko*; Ishibashi, Matsujiro*; Blaber, M.; Tokunaga, Masao*; Kuroki, Ryota

The crystal structure of halophilic $$beta$$-lactamase from ${it Chromohalobacter}$ sp.560 (HaBLA) was determined using X-ray crystallography. Moreover, the locations of bound Sr$$^{2+}$$ and Cs$$^{+}$$ ions were identified by anomalous X-ray diffraction. The location of one Cs$$^{+}$$ specific binding site was identified on HaBLA even in the presence of 9-fold molar excess of Na$$^{+}$$ (90 mM Na$$^{+}$$ /10 mM Cs$$^{+}$$). This Cs$$^{+}$$ binding site is formed by two main-chain O atoms and an aromatic ring of a side chain of Trp. An aromatic ring of Trp interacts with Cs$$^{+}$$ by the cation-$$pi$$ interaction. The observation of a selective and high-affinity Cs$$^{+}$$ binding site provides important information that is useful for designing artificial Cs$$^{+}$$ binding sites useful in bioremediation of radioactive isotopes.



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Category:Biochemical Research Methods



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