TY  - JOUR
A1  - Havelius, Kajsa G. V.
A1  - Reschke, Stefan
A1  - Horn, Sebastian
A1  - Doerlng, Alexander
A1  - Niks, Dimitri
A1  - Hille, Russ
A1  - Schulzke, Carola
A1  - Leimkühler, Silke
A1  - Haumann, Michael
T1  - Structure of the molybdenum site in YedY, a sulfite oxidase homologue from escherichia coli
JF  - Inorganic chemistry
N2  - YedY from Escherichia coil is a new member of the sulfite oxidase family of molybdenum cofactor (Moco)-containing oxidoreductases. We investigated the atomic structure of the molybdenum site in YedY by X-ray absorption spectroscopy, in comparison to human sulfite oxidase (hSO) and to a Mo(IV) model complex. The K-edge energy was indicative of Mo(V) in YedY, in agreement with X- and Q-band electron paramagnetic resonance results, whereas the hSO protein contained Mo(VI). In YedY and hSO, molybdenum is coordinated by two sulfur ligands from the molybdopterin ligand of the Moco, one thiolate sulfur of a cysteine (average Mo-S bond length of similar to 2.4 angstrom), and one (axial) oxo ligand (Mo=O, similar to 1.7 angstrom). hSO contained a second oxo group at Mo as expected, but in YedY, two species in about a 1:1 ratio were found at the active site, corresponding to an equatorial Mo-OH bond (similar to 2.1 angstrom) or possibly to a shorter M-O(-) bond. Yet another oxygen (or nitrogen) at a similar to 2.6 angstrom distance to Mo in YedY was identified, which could originate from a water molecule in the substrate binding cavity or from an amino acid residue close to the molybdenum site, i.e., Glu104, that is replaced by a glycine in hSO, or Asn45. The addition of the poor substrate dimethyl sulfoxide to YedY left the molybdenum coordination unchanged at high pH. In contrast, we found indications that the better substrate trimethylamine N-oxide and the substrate analogue acetone were bound at a similar to 2.6 angstrom distance to the molybdenum, presumably replacing the equatorial oxygen ligand. These findings were used to interpret the recent crystal structure of YedY and bear implications for its catalytic mechanism.
Y1  - 2011
U6  - https://doi.org/10.1021/ic101291j
SN  - 0020-1669
VL  - 50
IS  - 3
SP  - 741
EP  - 748
PB  - American Chemical Society
CY  - Washington
ER  -