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A complex iron-calcium cofactor catalyzing phosphotransfer chemistry.

A complex iron-calcium cofactor catalyzing phosphotransfer chemistry.

Science (New York, N.Y.) (2014-09-06)

Shee Chien Yong, Pietro Roversi, James Lillington, Fernanda Rodriguez, Martin Krehenbrink, Oliver B Zeldin, Elspeth F Garman, Susan M Lea, Ben C Berks

ABSTRACT

Alkaline phosphatases play a crucial role in phosphate acquisition by microorganisms. To expand our understanding of catalysis by this class of enzymes, we have determined the structure of the widely occurring microbial alkaline phosphatase PhoX. The enzyme contains a complex active-site cofactor comprising two antiferromagnetically coupled ferric iron ions (Fe(3+)), three calcium ions (Ca(2+)), and an oxo group bridging three of the metal ions. Notably, the main part of the cofactor resembles synthetic oxide-centered triangular metal complexes. Structures of PhoX-ligand complexes reveal how the active-site metal ions bind substrate and implicate the cofactor oxo group in the catalytic mechanism. The presence of iron in PhoX raises the possibility that iron bioavailability limits microbial phosphate acquisition.

MATERIALS

Product Number

Brand

Product Description

Iron, IRMM^®, certified reference material, 0.5 mm wire

Sigma-Aldrich

Phosphatase, Alkaline bovine, recombinant, expressed in Pichia pastoris, ≥4000 units/mg protein

Sigma-Aldrich

Iron, chips, 99.98% trace metals basis

Sigma-Aldrich

Iron, puriss. p.a., carbonyl-Iron powder, low in magnesium and manganese compounds, ≥99.5% (RT)

Sigma-Aldrich

Iron, powder, −325 mesh, 97%

Sigma-Aldrich

Iron, foil, thickness 0.1 mm, ≥99.9% trace metals basis

Sigma-Aldrich

Phosphatase, Alkaline from human placenta, ≥10 units/mg solid (in glycine buffer)

Iron, foil, not light tested, 100x100mm, thickness 0.006mm, 99.85%

Iron, foil, light tested, 25x25mm, thickness 0.015mm, 99.85%

Iron, foil, 10mm disks, thickness 0.038mm, hard, 99.5%

Iron, foil, 15mm disks, thickness 0.0125mm, 99.85%

Iron, foil, 15mm disks, thickness 0.006mm, 99.85%

Iron, foil, 15mm disks, thickness 0.020mm, 99.85%

Iron, foil, 10mm disks, thickness 0.25mm, as rolled, 99.99+%

Iron, foil, 10mm disks, thickness 0.38mm, hard, 99.5%

Iron, foil, 1m coil, thickness 0.38mm, hard, 99.5%

Iron, foil, 15mm disks, thickness 0.15mm, hard, 99.5%

Iron, foil, 20m coil, thickness 0.038mm, hard, 99.5%

Iron, foil, 10mm disks, thickness 0.075mm, as rolled, 99.99+%

Iron, foil, 1m coil, thickness 0.025mm, hard, 99.5%

Iron, foil, 15mm disks, thickness 0.008mm, 99.85%

Iron, foil, 15mm disks, thickness 0.125mm, hard, 99.5%

Iron, foil, 10mm disks, thickness 0.125mm, as rolled, 99.99+%

Iron, foil, 1m coil, thickness 0.05mm, hard, 99.5%

Iron, foil, 15mm disks, thickness 0.1mm, hard, 99.5%

Iron, foil, 15mm disks, thickness 0.038mm, hard, 99.5%

Iron, foil, 10mm disks, thickness 0.9mm, as rolled, 99.5%

Iron, foil, 10mm disks, thickness 0.075mm, hard, 99.5%

Iron, foil, 10mm disks, thickness 0.125mm, hard, 99.5%

Iron, foil, 1m coil, thickness 0.20mm, hard, 99.5%