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Bioelectrocatalysis of Sulfite Dehydrogenase from Sinorhizobium meliloti with Its Physiological Cytochrome Electron Partner
Author(s) -
Kalimuthu Palraj,
Hsiao JuChun,
Nair Remya Purushothaman,
Kappler Ulrike,
Bernhardt Paul V.
Publication year - 2017
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201700838
Subject(s) - sulfite , chemistry , cyclic voltammetry , cytochrome c , electron acceptor , inorganic chemistry , active site , catalysis , electrochemistry , organic chemistry , electrode , biochemistry , mitochondrion
We demonstrate electrochemically driven catalytic voltammetry of the Mo‐dependent sulfite dehydrogenase (SorT) from the α‐Proteobacterium Sinorhizobium meliloti with its physiological electron acceptor, the c ‐type cytochrome (SorU), with both proteins co‐adsorbed on a chemically modified Au working electrode. Both SorT and SorU were constrained under a perm‐selective dialysis membrane with the biopolymer chitosan as a co‐adsorbate, while the electrode was modified with a 3‐mercaptopropionate self‐assembled monolayer cast on the Au electrode. Cyclic voltammetry of the SorU protein reveals a well‐defined quasireversible Fe III/II redox couple at +130 mV versus NHE in 100 mM phosphate buffer solution (pH 7.0). Introduction of wild‐type sulfite dehydrogenase (SorT WT ) and sulfite transforms this transient SorU voltammetric response into a sigmoidal catalytic wave, which increases with sulfite concentration before eventually saturating. In addition to the wild‐type enzyme, the variants SorT R78K , SorT R78M , and SorT R78Q were also examined electrochemically in an effort to better understand the role of amino acid residue Arg78, which is in the vicinity of the Mo active site of SorT.