Crystal structure of the FTO protein reveals basis for its substrate specificity

摘要

Recent studies have unequivocally associated the fat mass and obesity-associated (FTO) gene with the risk of obesity. In vitro FTO protein is an AlkB-like DNA/RNA demethylase with a strong preference for 3-methylthymidine (3-meT) in single-stranded DNA or 3-methyluracil (3-meU) in single-stranded RNA. Here we report the crystal structure of FTO in complex with the mono-nucleotide 3-meT. FTO comprises an amino-terminal AlkB-like domain and a carboxy-terminal domain with a novel fold. Biochemical assays show that these two domains interact with each other, which is required for FTO catalytic activity. In contrast with the structures of other AlkB members, FTO possesses an extra loop covering one side of the conserved jelly-roll motif. Structural comparison shows that this loop selectively competes with the unmethylated strand of the DNA duplex for binding to FTO, suggesting that it has an important role in FTO selection against double-stranded nucleic acids. The ability of FTO to distinguish 3-meT or 3-meU from other nudeotides is conferred by its hydrogen-bonding interaction with the two carbonyl oxygen atoms in 3-meT or 3-meU. Taken together, these results provide a structural basis for understanding FTO substrate-specificity, and serve as a foundation for the rational design of FTO inhibitors.%“脂肪质和肥胖相关基因”(FTO)与体重增加及rn肥胖症风险相关。FTO蛋白是一种DNA/RNArn脱甲基酶，缺少它的小鼠异常消瘦。现在，人rnFTO的晶体结构在与单核苷酸3-meT形成的复rn合物中已被确定。该结构显示了这种蛋白区分rn单链和双链DNA的一个新颖机制。另外，生化rn分析表明，FTO的C-端(其功能以前未知)是rnFTO的催化活性所必需的，它通过与N-端催化rn域互动来发挥作用。这些结果为了解FTO基质rn特异性提供了一个结构基础，并目也为作为潜rn在抗肥胖药物的FTO抑制因子的合理设计奠定rn了基础。