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Updated: Aug 21, 2026

Site Specific Lysine Acetylation of Histones for Nucleosome Reconstitution using Genetic Code Expansion in Escherichia coli
Published on: December 26, 2020
Function of genetically encoded pyrrolysine in corrinoid-dependent methylamine methyltransferases
1Department of Microbiology, OSU Biochemistry Program, Ohio State University, Columbus, Ohio 43210, USA. krzycki.1@osu.edu
Abstract:
Methanogenesis from trimethylamine, dimethylamine or monomethylamine is initiated by a series of corrinoid-dependent methyltransferases. The non-homologous genes encoding the full-length methyltransferases each possess an in-frame UAG (amber) codon that does not terminate translation. The amber codon is decoded by a dedicated tRNA, and corresponds to the novel amino acid pyrrolysine in one of the methyltransferases, indicating pyrrolysine to be the 22nd genetically encoded amino acid. Pyrrolysine has the structure of lysine with the (epsilon)N in amide linkage with a pyrroline ring. The reactivity of the electrophilic imine bond is the basis for the proposed function of pyrrolysine in activating and optimally orienting methylamine for methyl transfer to the cobalt ion of a cognate corrinoid protein. This reaction is essential for methane formation from methylamines, and may underlie the retention of pyrrolysine in the genetic code of methanogens.
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