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

Arai S, Yonezawa Y, Okazaki N, Matsumoto F, Shibazaki C, Shimizu R, Yamada M, Adachi M, Tamada T, Kawamoto M, Tokunaga H, Ishibashi M, Blaber M, Tokunaga M, Kuroki R - Acta Crystallogr. D Biol. Crystallogr. (2015)

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Quantum Beam Science Directorate, Japan Atomic Energy Agency, 2-4 Shirakata-shirane, Tokai, Ibaraki 319-1195, Japan.

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 β-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.

Show MeSH
The overall structure of NQ-HaBLA. The asymmetric units of NQ-HaBLA from (a) condition 1B (75 mM Na+/25 mM Cs+) and (b) condition 2A (0 mM Ca2+/200 mM Sr2+) are shown. Chains A, B and C are coloured red, blue and green, respectively. The orange, magenta and cyan spheres show Ca2+, Sr2+ and Cs+, respectively. (c) Sr2+-bound and Cs+-bound structure of NQ-HaBLA, in which Sr2+ and Cs+ observed around chains A, B and C in condition 1B and condition 2A are integrated into a single molecule of NQ-HaBLA. The residues recognizing Sr2+ and Cs+ are shown as blue sticks. The active-site residues are shown as yellow sticks.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4356365&req=5

fig1: The overall structure of NQ-HaBLA. The asymmetric units of NQ-HaBLA from (a) condition 1B (75 mM Na+/25 mM Cs+) and (b) condition 2A (0 mM Ca2+/200 mM Sr2+) are shown. Chains A, B and C are coloured red, blue and green, respectively. The orange, magenta and cyan spheres show Ca2+, Sr2+ and Cs+, respectively. (c) Sr2+-bound and Cs+-bound structure of NQ-HaBLA, in which Sr2+ and Cs+ observed around chains A, B and C in condition 1B and condition 2A are integrated into a single molecule of NQ-HaBLA. The residues recognizing Sr2+ and Cs+ are shown as blue sticks. The active-site residues are shown as yellow sticks.

Mentions: The crystallization of WT-HaBLA and NQ-HaBLA required divalent metal ions (Mg2+ or Ca2+). Both WT-HaBLA and NQ-HaBLA crystallized isomorphously, and both contained three HaBLA molecules in the asymmetric unit. The overall structure of Ca2+-bound and Cs+-bound NQ-HaBLA from condition 1B (75 mM Na+/25 mM Cs+) determined at 1.8 Å resolution and Sr2+-bound NQ-HaBLA from condition 2A (0 mM Ca2+/200 mM Sr2+) determined at 1.9 Å resolution are shown in Fig. 1 ▶.


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

Arai S, Yonezawa Y, Okazaki N, Matsumoto F, Shibazaki C, Shimizu R, Yamada M, Adachi M, Tamada T, Kawamoto M, Tokunaga H, Ishibashi M, Blaber M, Tokunaga M, Kuroki R - Acta Crystallogr. D Biol. Crystallogr. (2015)

The overall structure of NQ-HaBLA. The asymmetric units of NQ-HaBLA from (a) condition 1B (75 mM Na+/25 mM Cs+) and (b) condition 2A (0 mM Ca2+/200 mM Sr2+) are shown. Chains A, B and C are coloured red, blue and green, respectively. The orange, magenta and cyan spheres show Ca2+, Sr2+ and Cs+, respectively. (c) Sr2+-bound and Cs+-bound structure of NQ-HaBLA, in which Sr2+ and Cs+ observed around chains A, B and C in condition 1B and condition 2A are integrated into a single molecule of NQ-HaBLA. The residues recognizing Sr2+ and Cs+ are shown as blue sticks. The active-site residues are shown as yellow sticks.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4356365&req=5

fig1: The overall structure of NQ-HaBLA. The asymmetric units of NQ-HaBLA from (a) condition 1B (75 mM Na+/25 mM Cs+) and (b) condition 2A (0 mM Ca2+/200 mM Sr2+) are shown. Chains A, B and C are coloured red, blue and green, respectively. The orange, magenta and cyan spheres show Ca2+, Sr2+ and Cs+, respectively. (c) Sr2+-bound and Cs+-bound structure of NQ-HaBLA, in which Sr2+ and Cs+ observed around chains A, B and C in condition 1B and condition 2A are integrated into a single molecule of NQ-HaBLA. The residues recognizing Sr2+ and Cs+ are shown as blue sticks. The active-site residues are shown as yellow sticks.
Mentions: The crystallization of WT-HaBLA and NQ-HaBLA required divalent metal ions (Mg2+ or Ca2+). Both WT-HaBLA and NQ-HaBLA crystallized isomorphously, and both contained three HaBLA molecules in the asymmetric unit. The overall structure of Ca2+-bound and Cs+-bound NQ-HaBLA from condition 1B (75 mM Na+/25 mM Cs+) determined at 1.8 Å resolution and Sr2+-bound NQ-HaBLA from condition 2A (0 mM Ca2+/200 mM Sr2+) determined at 1.9 Å resolution are shown in Fig. 1 ▶.

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Quantum Beam Science Directorate, Japan Atomic Energy Agency, 2-4 Shirakata-shirane, Tokai, Ibaraki 319-1195, Japan.

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 β-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.

Show MeSH