Title
Methane generation via intraprotein C–S bond cleavage in cytochrome b562 reconstituted with nickel didehydrocorrin
Author
Yuta Miyazaki, Koji Oohora, Takashi Hayashi
Year
2019
Journal
Journal of Organometallic Chemistry
Abstract
Cytochrome b562 (Cyt b562) reconstituted with nickel didehydrocorrin (NiII(DDHC)), a protein-based functional model of methyl-coenzyme M reductase (MCR), was investigated to demonstrate methane generation via intraprotein cleavage of a C–S bond. NiII(DDHC) was synthesized as a model complex of an MCR cofactor known as F430 and found to show NiII/NiI redox behavior with a potential of −0.61 V vs. Ag|AgCl. This potential is slightly positive-shifted compared to that of F430 without protein. Conjugation of NiII(DDHC) with the apo-form of Cyt b562 provides reconstituted Cyt b562 (rCyt b562(NiII(DDHC))) which was characterized by spectroscopic measurements. Photoirradiation of rCyt b562(NiII(DDHC)) generates methane gas in the presence of tris(2,2′-bipyridine)ruthenium(II) chloride as a photosensitizer and sodium ascorbate as a sacrificial reagent. Further experiments using Cyt b562 mutants indicate that methane is derived from the CH3S group of the methionine residue in the heme-binding site where thioether, thiol and the nickel center are precisely arranged. The present study demonstrates the first example of methane generation via intraprotein cleavage of a C–S bond using a functional model of MCR.
Instrument
V-670, J-820
Keywords
Circular dichroism, Secondary structure, Protein folding, Ligand binding, Coordination chemistry, Absorption, Protein structure, Biochemistry