Packianathan Charles, Pillai Jitesh K, Riaz Ahmed, Kandavelu Palani, Sankaran Banumathi, Rosen Barry P
Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA.
SER-CAT and the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA.
Acta Crystallogr F Struct Biol Commun. 2014 Oct;70(Pt 10):1385-8. doi: 10.1107/S2053230X14018469. Epub 2014 Sep 25.
Arsenic is one the most toxic environmental substances. Arsenic is ubiquitous in water, soil and food, and ranks first on the Environmental Protection Agency's Superfund Priority List of Hazardous Substances. Arsenic(III) S-adenosylmethionine methyltransferases (AS3MT in animals and ArsM in microbes) are key enzymes of arsenic biotransformation, catalyzing the methylation of inorganic arsenite to give methyl, dimethyl and trimethyl products. Arsenic methyltransferases are found in members of every kingdom from bacteria to humans (EC 2.1.1.137). In the human liver, hAS3MT converts inorganic arsenic into more toxic and carcinogenic forms. CrArsM, an ortholog of hAS3MT from the eukaryotic green alga Chlamydomonas reinhardtii, was purified by chemically synthesizing the gene and expressing it in Escherichia coli. Synthetic purified CrArsM was crystallized in an unliganded form. Crystals were obtained by the hanging-drop vapor-diffusion method. The crystals belonged to space group R3:H, with unit-cell parameters a = b = 157.8, c = 95.4 Å, γ = 120° and two molecules in the asymmetric unit. Complete data sets were collected and processed to a resolution of 2.40 Å.
砷是毒性最强的环境物质之一。砷在水、土壤和食物中广泛存在，在环境保护局的有害物质超级基金优先名单上排名第一。砷（III）S-腺苷甲硫氨酸甲基转移酶（动物中的AS3MT和微生物中的ArsM）是砷生物转化的关键酶，催化无机亚砷酸盐甲基化生成甲基、二甲基和三甲基产物。从细菌到人类的每个生物界成员中都发现了砷甲基转移酶（EC 2.1.1.137）。在人类肝脏中，hAS3MT将无机砷转化为毒性和致癌性更强的形式。来自真核绿藻莱茵衣藻的hAS3MT直系同源物CrArsM，通过化学合成基因并在大肠杆菌中表达进行纯化。合成纯化的CrArsM以无配体形式结晶。通过悬滴气相扩散法获得晶体。晶体属于空间群R3:H，晶胞参数a = b = 157.8，c = 95.4 Å，γ = 120°，不对称单位中有两个分子。收集完整数据集并处理至2.40 Å分辨率。
