The functions of crucial cysteine residues in the arsenite methylation catalyzed by recombinant human arsenic (III) methyltransferase.

Article Details

Citation

Copy to clipboard

Wang S, Geng Z, Shi N, Li X, Wang Z

The functions of crucial cysteine residues in the arsenite methylation catalyzed by recombinant human arsenic (III) methyltransferase.

PLoS One. 2014 Oct 28;9(10):e110924. doi: 10.1371/journal.pone.0110924. eCollection 2014.

PubMed ID

25349987 [ View in PubMed

]

Abstract

Arsenic (III) methyltransferase (AS3MT) is a cysteine (Cys)-rich enzyme that catalyzes the biomethylation of arsenic. To investigate how these crucial Cys residues promote catalysis, we used matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS) to analyze Cys residues in recombinant human arsenic (III) methyltransferase (hAS3MT). We detected two disulfide bonds, Cys250-Cys32 and Cys368-Cys369, in hAS3MT. The Cys250-Cys32 disulfide bond was reduced by glutathione (GSH) or other disulfide bond reductants before the enzymatic methylation of arsenite (iAs3+). In addition to exposing residues around the active sites, cleavage of the Cys250-Cys32 pair modulated the conformation of hAS3MT. This adjustment may stabilize the binding of S-Adenosyl-L-methionine (AdoMet) and favor iAs3+ binding to hAS3MT. Additionally, we observed the intermediate of Cys250-S-adenosylhomocysteine (AdoHcy), suggesting that Cys250 is involved in the transmethylation. In recovery experiments, we confirmed that trivalent arsenicals were substrates for hAS3MT, methylation of arsenic occurred on the enzyme, and an intramolecular disulfide bond might be formed after iAs3+ was methylated to dimethylarsinous acid (DMA3+). In this work, we clarified both the functional roles of GSH and the crucial Cys residues in iAs3+ methylation catalyzed by hAS3MT.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Ademetionine	Arsenite methyltransferase	Protein	Humans	Unknown	Not Available	Details