SOEs (sulfite-oxidizing enzymes) are physiologically vital and occur in all forms of life. During the catalytic cycle, the five-co-ordinate square pyramidal oxo-molybdenum active site passes through the Mo(V) state, and intimate details of the structure can be obtained from variable frequency pulsed EPR spectroscopy through the hyperfine and nuclear quadrupole interactions of nearby magnetic nuclei. By employing variable spectrometer operational frequencies, it is possible to optimize the measurement conditions for difficult quadrupolar nuclei of interest (e.g. (17)O, (33)S, (35)Cl and (37)Cl) and to simplify the interpretation of the spectra. Isotopically labelled model Mo(V) compounds provide further insight into the electronic and geometric structures and chemical reactions of the enzymes. Recently, blocked forms of SOEs having co-ordinated sulfate, the reaction product, were detected using (33)S (I=3/2) labelling. This blocking of product release is a possible contributor to fatal human sulfite oxidase deficiency in young children.
Download full-text PDF |
Source |
|---|---|
| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2613767 | PMC |
| http://dx.doi.org/10.1042/BST0361129 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Structural and Spectroscopic Investigations of pH-Dependent Mo(V) Species in a Bacterial Sulfite-Oxidizing Enzyme.
Inorg Chem
December 2024
Aix Marseille Univ, CNRS, BIP UMR7281, IMM, IM2B, Marseille 13009, France.
Mono-pyranopterin-containing sulfite-oxidizing enzymes (SOEs), including eukaryotic sulfite oxidases and homologous prokaryotic sulfite dehydrogenases (SDHs), are molybdenum enzymes that exist in almost all forms of life, where they catalyze the direct oxidation of sulfite into sulfate, playing a key role in protecting cells and organisms against sulfite-induced damage. To decipher their catalytic mechanism, we have previously provided structural and spectroscopic evidence for direct coordination of HPO to the Mo atom at the active site of the SDH from the hyperthermophilic bacterium (SDH), mimicking the proposed sulfate-bound intermediate proposed to be formed during catalysis. In this work, by solving the X-ray crystallographic structure of the unbound enzyme, we resolve the changes in the hydrogen bonding network in the molybdenum environment that enable the stabilization of the previously characterized phosphate adduct.
View Article and Find Full Text PDFAddressing Ligand-Based Redox in Molybdenum-Dependent Methionine Sulfoxide Reductase.
J Am Chem Soc
February 2020
Department of Chemistry and Chemical Biology , The University of New Mexico , MSC03 2060, 1 University of New Mexico, Albuquerque , New Mexico 87131-0001 , United States.
A combination of pulsed EPR, CW EPR, and X-ray absorption spectroscopies has been employed to probe the geometric and electronic structure of the periplasmic molybdenum-dependent methionine sulfoxide reductase (MsrP). O and H pulsed EPR spectra show that the Mo(V) enzyme form does not possess an exchangeable HO/OH ligand bound to Mo as found in the sulfite oxidizing enzymes of the same family. The nature of the unusual CW EPR spectrum has been re-evaluated in light of new data on the MsrP-N45R variant and related small-molecule analogues of the active site.
View Article and Find Full Text PDFIdentification of a 119-bp Promoter of the Maize Sulfite Oxidase Gene () That Confers High-Level Gene Expression and ABA or Drought Inducibility in Transgenic Plants.
Int J Mol Sci
July 2019
College of Life Science, Henan Agricultural University, Zhengzhou 450002, China.
Drought adversely affects crop growth and yields. The cloning and characterization of drought- or abscisic acid (ABA)-inducible promoters is of great significance for their utilization in the genetic improvement of crop resistance. Our previous studies have shown that maize sulfite oxidase (SO) has a sulfite-oxidizing function and is involved in the drought stress response.
View Article and Find Full Text PDFControl of Bacterial Sulfite Detoxification by Conserved and Species-Specific Regulatory Circuits.
Front Microbiol
May 2019
Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, Australia.
Although sulfite, a by-product of the degradation of many sulfur compounds, is highly reactive and can cause damage to DNA, proteins and lipids, comparatively little is known about the regulation of sulfite-oxidizing enzyme (SOEs) expression. Here we have investigated the regulation of SOE-encoding genes in two species of α-Proteobacteria, and , that degrade organo- and inorganic sulfur compounds, respectively, and contain unrelated types of SOEs that show different expression patterns. Our work revealed that in both cases, the molecular signal that triggers SOE gene expression is sulfite, and strong up-regulation depends on the presence of a sulfite-responsive, cognate Extracytoplasmic function (ECF) sigma factor, making sulfite oxidation a bacterial stress response.
View Article and Find Full Text PDFThe central active site arginine in sulfite oxidizing enzymes alters kinetic properties by controlling electron transfer and redox interactions.
Biochim Biophys Acta Bioenerg
January 2018
Centre for Metals in Biology, School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD 4072, Australia. Electronic address:
A central conserved arginine, first identified as a clinical mutation leading to sulfite oxidase deficiency, is essential for catalytic competency of sulfite oxidizing molybdoenzymes, but the molecular basis for its effects on turnover and substrate affinity have not been fully elucidated. We have used a bacterial sulfite dehydrogenase, SorT, which lacks an internal heme group, but transfers electrons to an external, electron accepting cytochrome, SorU, to investigate the molecular functions of this arginine residue (Arg78). Assay of the SorT Mo centre catalytic competency in the absence of SorU showed that substitutions in the central arginine (R78Q, R78K and R78M mutations) only moderately altered SorT catalytic properties, except for R78M which caused significant reduction in SorT activity.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!