4rsr

ArsM arsenic(III) S-adenosylmethionine methyltransferase with trivalent phenyl arsencial derivative-Roxarsone

spinqualitylabelsall models 4rsr, resolution 2.25Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4rsr is a 1 chain structure with sequence from Cyanidioschyzon sp. 5508. This structure supersedes the now removed PDB entry 4ku9. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: CA, DTT, MG, NA, RXO Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function C0JV69_9RHOD Publication Abstract from PubMed Methylation of the toxic metalloid arsenic is widespread in nature. Members of every kingdom have arsenic(III) S-adenosylmethionine (SAM) methyltransferase enzymes, which are termed ArsM in microbes and AS3MT in animals, including humans. Trivalent arsenic(III) is methylated up to three times to form methylarsenite [MAs(III)], dimethylarsenite [DMAs(III)] and the volatile trimethylarsine [TMAs(III)]. In microbes, arsenic methylation is a detoxification process. In humans, MAs(III) and DMAs(III) are more toxic and carcinogenic than either inorganic arsenate or arsenite. Here, new crystal structures are reported of ArsM from the thermophilic eukaryotic alga Cyanidioschyzon sp. 5508 (CmArsM) with the bound aromatic arsenicals phenylarsenite [PhAs(III)] at 1.80 A resolution and reduced roxarsone [Rox(III)] at 2.25 A resolution. These organoarsenicals are bound to two of four conserved cysteine residues: Cys174 and Cys224. The electron density extends the structure to include a newly identified conserved cysteine residue, Cys44, which is disulfide-bonded to the fourth conserved cysteine residue, Cys72. A second disulfide bond between Cys72 and Cys174 had been observed previously in a structure with bound SAM. The loop containing Cys44 and Cys72 shifts by nearly 6.5 A in the arsenic(III)-bound structures compared with the SAM-bound structure, which suggests that this movement leads to formation of the Cys72-Cys174 disulfide bond. A model is proposed for the catalytic mechanism of arsenic(III) SAM methyltransferases in which a disulfide-bond cascade maintains the products in the trivalent state. A disulfide-bond cascade mechanism for arsenic(III) S-adenosylmethionine methyltransferase.,Marapakala K, Packianathan C, Ajees AA, Dheeman DS, Sankaran B, Kandavelu P, Rosen BP Acta Crystallogr D Biol Crystallogr. 2015 Mar 1;71(Pt 3):505-15. doi:, 10.1107/S1399004714027552. Epub 2015 Feb 26. PMID:25760600 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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