The central active site arginine in sulfite oxidizing enzymes alters kinetic properties by controlling electron transfer and redox interactions
Ju-Chun Hsiao, Aaron P McGrath, Linda Kielmann, Palraj Kalimuthu, Farzana Darain, Paul V Bernhardt, Jeffrey Harmer, Mihwa Lee, Kimberley Meyers, Megan J Maher, Ulrike Kappler
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS | ELSEVIER SCIENCE BV | Published : 2018
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..View full abstract
Awarded by ARC
This study was supported by the ARC Australian Research Fellowship and grant (DP0878525) to UK and Discovery Project Grant (DP150103345) to PVB. Aspects of this research were undertaken on the Macromolecular Crystallography beamline MX2 at the Australian Synchrotron (Victoria, Australia) and we thank the beamline staff for their enthusiastic and professional support.