C-methylation of aromatic small molecules by C-methyltransferases (C-MTs) is an important biological transformation that involves C–C bond formation using S-adenosyl-l-methionine (SAM) as the methyl donor. Here, two advances in the mechanistic understanding of C-methylation of the 8-position of coumarin substrates catalyzed by the C-MT NovO from Streptomyces spheroides are described. First, a crystal structure of NovO reveals the Arg116-Asn117 and His120-Arg121 motifs are essential for coumarin substrate binding. Second, the active-site His120 is responsible for deprotonation of the phenolic 7-hydroxyl group on the coumarin substrate, activating the rate-determining methyl transfer step from SAM. This work expands our mechanistic knowledge of C-MTs, which could be used in the downstream development of engineered biocatalysts for small molecule C-alkylations.
- aromatic small molecules
Sadler, J. C., Chung, C. H., Mosley, J. E., Burley, G. A., & Humphreys, L. D. (2017). Structural and functional basis of C-methylation of coumarin scaffolds by NovO. ACS Chemical Biology, 12(2), 374-379. https://doi.org/10.1021/acschembio.6b01053