Intraprotein transmethylation via a CH3-Co(iii) species in myoglobin reconstituted with a cobalt corrinoid complex

Yoshitsugu Morita, Koji Oohora, Akiyoshi Sawada, Kazuki Doitomi, Jun Ohbayashi, Takashi Kamachi, Kazunari Yoshizawa, Yoshio Hisaeda, Takashi Hayashi

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Abstract

Myoglobin reconstituted with a cobalt tetradehydrocorrin derivative, rMb(Co(TDHC)), was investigated as a hybrid model to replicate the reaction catalyzed by methionine synthase. In the heme pocket, CoI(TDHC) is found to react with methyl iodide to form the methylated cobalt complex, CH3-CoIII(TDHC), although it is known that a similar nucleophilic reaction of a cobalt(i) tetradehydrocorrin complex does not proceed effectively in organic solvents. Furthermore, we observed a residue- and regio-selective transmethylation from the CH3-CoIII(TDHC) species to the Nε2 atom of the His64 imidazole ring in myoglobin at 25 °C over a period of 48 h. These findings indicate that the protein matrix promotes the model reaction of methionine synthase via the methylated cobalt complex. A theoretical calculation provides support for a plausible reaction mechanism wherein the axial histidine ligation stabilizes the methylated cobalt complex and subsequent histidine-flipping induces the transmethylation via heterolytic cleavage of the Co-CH3 bond in the hybrid model.

Original languageEnglish
Pages (from-to)3277-3284
Number of pages8
JournalDalton Transactions
Volume45
Issue number8
DOIs
Publication statusPublished - Jan 1 2016

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All Science Journal Classification (ASJC) codes

  • Inorganic Chemistry

Cite this

Morita, Y., Oohora, K., Sawada, A., Doitomi, K., Ohbayashi, J., Kamachi, T., ... Hayashi, T. (2016). Intraprotein transmethylation via a CH3-Co(iii) species in myoglobin reconstituted with a cobalt corrinoid complex. Dalton Transactions, 45(8), 3277-3284. https://doi.org/10.1039/c5dt04109k