4UY5: Crystal Structure Of Histidine-specific Methyltransferase Egtd From Mycobacterium Smegmatis

Citation:
Abstract
EgtD 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.
PDB ID: 4UY5Download
MMDB ID: 123715
PDB Deposition Date: 2014/8/29
Updated in MMDB: 2014/10
Experimental Method:
x-ray diffraction
Resolution: 2  Å
Source Organism:
Similar Structures:
Biological Unit for 4UY5: monomeric; determined by author and by software (PISA)
Molecular Components in 4UY5
Label Count Molecule
Protein (1 molecule)
1
Histidine-specific Methyltransferase Egtd(Gene symbol: MSMEG_6247)
Molecule annotation
Chemicals (2 molecules)
1
1
2
1
* Click molecule labels to explore molecular sequence information.

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