National Institute of Biological Sciences, No. 7 Science Park Road, Beijing 102206, China.
Nature. 2010 Apr 22;464(7292):1205-9. doi: 10.1038/nature08921. Epub 2010 Apr 7.
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 mononucleotide 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 nucleotides 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.
最近的研究明确将脂肪量和肥胖相关（FTO）基因与肥胖风险联系起来。体外 FTO 蛋白是一种 AlkB 样 DNA/RNA 去甲基酶，对单链 DNA 中的 3-甲基胸腺嘧啶（3-meT）或单链 RNA 中的 3-甲基尿嘧啶（3-meU）具有强烈的偏好。本文报道了 FTO 与单核苷酸 3-meT 复合物的晶体结构。FTO 由氨基端 AlkB 样结构域和羧基端具有新颖折叠的结构域组成。生化分析表明，这两个结构域相互作用，这是 FTO 催化活性所必需的。与其他 AlkB 成员的结构不同，FTO 具有一个额外的环，覆盖保守的果冻卷基序的一侧。结构比较表明，该环选择性地与 DNA 双链体的未甲基化链竞争结合 FTO，表明它在 FTO 对双链核酸的选择中具有重要作用。FTO 区分 3-meT 或 3-meU 与其他核苷酸的能力是由其与 3-meT 或 3-meU 中的两个羰基氧原子的氢键相互作用赋予的。总之，这些结果为理解 FTO 底物特异性提供了结构基础，并为 FTO 抑制剂的合理设计提供了基础。
