109309-22-0Relevant academic research and scientific papers
Structural studies of the molybdenum center of the pathogenic R160Q mutant of human sulfite oxidase by pulsed EPR spectroscopy and 17O and 33S labeling
Astashkin, Andrei V.,Johnson-Winters, Kayunta,Klein, Eric L.,Feng, Changjian,Wilson, Heather L.,Rajagopalan,Raitsimring, Arnold M.,Enemark, John H.
, p. 8471 - 8480 (2008)
Electron paramagnetic resonance (EPR) investigation of the Mo(V) center of the pathogenic R16OQ mutant of human sulfite oxidase (hSO) confirms the presence of three distinct species whose relative abundances depend upon pH. Species 1 is exclusively present at pH ≤ 6, and remains in significant amounts even at pH 8. Variable-frequency electron spin echo envelope modulation (ESEEM) studies of this species prepared with 33S-labeled sulfite clearly show the presence of coordinated sulfate, as has previously been found for the blocked form of Arabidopsis thaliana at low pH (Astashkin, A. V.; Johnson-Winters, K.; Klein, E. L.; Byrne, R. S.; Hille, R.; Raitsimring, A. M.; Enemark, J. H. J. Am. Chem. Soc. 2007, 129, 14800). The ESEEM spectra of Species 1 prepared in 17O-enriched water show both strongly and weakly magnetically coupled 17O atoms that can be assigned to an equatorial sulfate ligand and the axial oxo ligand, respectively. The nuclear quadrupole interaction (nqi) of the axial oxo ligand is substantially stronger than those found for other oxo-Mo(V) centers studied previously. Additionally, pulsed electron-nuclear double resonance (ENDOR) measurements reveal a nearby weakly coupled exchangeable proton. The structure for Species 1 proposed from the pulsed EPR results using isotopic labeling is a six-coordinate Mo(V) center with an equatorial sulfate ligand that is hydrogen bonded to an exchangeable proton. Six-coordination is supported by the 17O nqi parameters for the axial oxo group of the model compound, (dttd)Mo17O( 17Otms), where H2dttd = 2,3:8,9-dibenzo-1,4,7,10- tetrathiadecane; tms = trimethylsilyl. Reduction of R160Q to Mo(V) with Ti(III) gives primarily Species 2, another low pH form, whereas reduction with sulfite at higher pH values gives a mixture of Species 1 and 2, as well as the primary high pH form of wild-type SO. The occurrence of significant amounts of the sulfate-blocked form of R160Q (Species 1) at physiological pH suggests that this species may be a contributing factor to the lethality of this mutation.
Molybdenum(VI) and Molybdenum(V) Complexes with N,N'-Dimethyl-N,N'-bis(2-mercaptophenyl)ethylenediamine. Electrochemical and Electron Paramagnetic Resonance Models for the Molybdenum(VI/V) Centers of the Molybdenum Hydroxylases and Related Enzymes
Dowerah, Dulal,Spence, Jack T.,Singh, Raghuvir,Wedd, Anthony G.,Wilson, Graham L.,et al.
, p. 5655 - 5665 (2007/10/02)
As models for the molybdenum(VI/V) centers of the molybdenum hydroxylases and related enzymes, MoO2L and MoOClL (LH2=N,N'-dimethyl-N,N'-bis(2-mercaptophenyl)ethylenediamine) have been synthesized.The structure of MoO2L hasbeen determined by X-ray crystallography.The compound crystallizes in space group P21/n, with a=10.049(2) Angstroem, b=14.538(2) Angstroem, c=12.143(1) Angstroem, β=103.73(1) deg, and Z=4.MoO2L is six-coordinate with approximate C2 symmetry, with the two thiolate S atoms trans to one another and the two tertiary amine N atoms approximately trans to the terminal oxo groups.MoO2L undergoes reversible one-electron reduction on both cyclic voltammetric and coulometric time scales to give various oxo-Mo(V) complexes.The EPR spectra of these complexes including 98Mo, 2H, and 17O substituted species, are consistent with formulation as -, cis-MoO(OH)L, -, and cis-MoO(SH)L. 1H coupling constants for cis-MoO(OH)L (1.65 mT) and cis-MoO(SH)L (1.05 mT) and the 17O coupling constants for Mo17O(17OH)L (0.25 and 0.82 mT), - (0.43 mT), and Mo17O(SH)L (0.22 mT) have been measured.MoOClL exhibit reversible one-electron electrochemical reduction in its cyclic voltammogram but decomposes upon coulometric reduction.EPR data indicate it is trans-MoOClL.Substitution of Cl- by OH-, F-, and SH- has been effected in solution.The implications of the results for the structures of Mo(VI/V) centers of the enzymes are discussed.In particular, MoVOS(OR) and MoVO(SH)(OR) (OR=bound product) are suggested as the centers responsible for the "very rapid" and "rapid" EPR signals of xanthine oxidase.An MoVO(OH) center appears to be involved in the "slow" EPR signal of xanthine oxidase and the low pH forms of sulfite axidase and nitrate reductase; the high pH forms of the latter enzymes, however, do not apear to involve a conjugate base MoVO2 center.
