Dataset Information

Structure of a highly acidic ?-lactamase from the moderate halophile Chromohalobacter sp. 560 and the discovery of a Cs(+)-selective binding site.

ABSTRACT: Environmentally friendly absorbents are needed for Sr(2+) and Cs(+), as the removal of the radioactive Sr(2+) and Cs(+) that has leaked from the Fukushima Nuclear Power Plant is one of the most important problems in Japan. Halophilic proteins are known to have many acidic residues on their surface that can provide specific binding sites for metal ions such as Cs(+) or Sr(2+). The crystal structure of a halophilic ?-lactamase from Chromohalobacter sp. 560 (HaBLA) was determined to resolutions of between 1.8 and 2.9?Å in space group P31 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 in HaBLA even in the presence of a ninefold molar excess of Na(+) (90?mM Na(+)/10?mM Cs(+)). From an activity assay using isothermal titration calorimetry, the bound Sr(2+) and Cs(+) ions do not significantly affect the enzymatic function of HaBLA. The observation of a selective and high-affinity Cs(+)-binding site provides important information that is useful for the design of artificial Cs(+)-binding sites that may be useful in the bioremediation of radioactive isotopes.

SUBMITTER: Arai S

PROVIDER: S-EPMC4356365 | biostudies-literature | 2015 Mar

REPOSITORIES: biostudies-literature

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Structure of a highly acidic β-lactamase from the moderate halophile Chromohalobacter sp. 560 and the discovery of a Cs(+)-selective binding site.

Arai Shigeki S Yonezawa Yasushi Y Okazaki Nobuo N Matsumoto Fumiko F Shibazaki Chie C Shimizu Rumi R Yamada Mitsugu M Adachi Motoyasu M Tamada Taro T Kawamoto Masahide M Tokunaga Hiroko H Ishibashi Matsujiro M Blaber Michael M Tokunaga Masao M Kuroki Ryota R

Acta crystallographica. Section D, Biological crystallography 20150226 Pt 3

Environmentally friendly absorbents are needed for Sr(2+) and Cs(+), as the removal of the radioactive Sr(2+) and Cs(+) that has leaked from the Fukushima Nuclear Power Plant is one of the most important problems in Japan. Halophilic proteins are known to have many acidic residues on their surface that can provide specific binding sites for metal ions such as Cs(+) or Sr(2+). The crystal structure of a halophilic β-lactamase from Chromohalobacter sp. 560 (HaBLA) was determined to resolutions of ...[more]

PMID: 25760604

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Project description:Members of the genus Spiribacter are found worldwide and are abundant in ecosystems possessing intermediate salinities between seawater and saturated salt concentrations. Spiribacter salinus M19-40 is the type species of this genus and its first cultivated representative. In the habitats of S. salinus M19-40, high salinity is a key determinant for growth and we therefore focused on the cellular adjustment strategy to this persistent environmental challenge. We coupled these experimental studies to the in silico mining of the genome sequence of this moderate halophile with respect to systems allowing this bacterium to control its potassium and sodium pools, and its ability to import and synthesize compatible solutes. S. salinus M19-40 produces enhanced levels of the compatible solute ectoine, both under optimal and growth-challenging salt concentrations, but the genes encoding the corresponding biosynthetic enzymes are not organized in a canonical ectABC operon. Instead, they are scrambled (ectAC; ectB) and are physically separated from each other on the S. salinus M19-40 genome. Genomes of many phylogenetically related bacteria also exhibit a non-canonical organization of the ect genes. S. salinus M19-40 also synthesizes trehalose, but this compatible solute seems to make only a minor contribution to the cytoplasmic solute pool under osmotic stress conditions. However, its cellular levels increase substantially in stationary phase cells grown under optimal salt concentrations. In silico genome mining revealed that S. salinus M19-40 possesses different types of uptake systems for compatible solutes. Among the set of compatible solutes tested in an osmostress protection growth assay, glycine betaine and arsenobetaine were the most effective. Transport studies with radiolabeled glycine betaine showed that S. salinus M19-40 increases the pool size of this osmolyte in a fashion that is sensitively tied to the prevalent salinity of the growth medium. It was amassed in salt-stressed cells in unmodified form and suppressed the synthesis of ectoine. In conclusion, the data presented here allow us to derive a genome-scale picture of the cellular adjustment strategy of a species that represents an environmentally abundant group of ecophysiologically important halophilic microorganisms.

Dataset Information

Structure of a highly acidic ?-lactamase from the moderate halophile Chromohalobacter sp. 560 and the discovery of a Cs(+)-selective binding site.

Publications

Structure of a highly acidic β-lactamase from the moderate halophile Chromohalobacter sp. 560 and the discovery of a Cs(+)-selective binding site.

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