Structural highlights
FunctionEGTD_MYCS2 Catalyzes the methylations of histidine to form N-alpha,N-alpha,N-alpha-trimethyl-L-histidine (also known as hercynine). Histidine and alpha-N,N-dimethylhistidine are preferred substrates.[1] Publication Abstract from PubMedEgtD is an S-adenosyl-l-methionine (SAM)-dependent histidine N,N,N-methyltransferase that catalyzes the formation of hercynine from histidine in the ergothioneine biosynthetic process of Mycobacterium smegmatis. Ergothioneine is a secreted antioxidant that protects mycobacterium from oxidative stress. Here, we present three crystal structures of EgtD in the apo form, the histidine-bound form, and the S-adenosyl-l-homocysteine (SAH)/histidine-bound form. The study revealed that EgtD consists of two distinct domains: a typical methyltransferase domain and a unique substrate binding domain. The histidine binding pocket of the substrate binding domain primarily recognizes the imidazole ring and carboxylate group of histidine rather than the amino group, explaining the high selectivity for histidine and/or (mono-, di-) methylated histidine as substrates. In addition, SAM binding to the MTase domain induced a conformational change in EgtD to facilitate the methyl transfer reaction. The structural analysis provides insights into the putative catalytic mechanism of EgtD in a processive trimethylation reaction. Structural insights into the histidine trimethylation activity of EgtD from Mycobacterium smegmatis.,Jeong JH, Cha HJ, Ha SC, Rojviriya C, Kim YG Biochem Biophys Res Commun. 2014 Oct 3;452(4):1098-103. doi:, 10.1016/j.bbrc.2014.09.058. Epub 2014 Sep 22. PMID:25251321[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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