State Key Laboratory of Bio-Membrane and Membrane Biotechnology, Tsinghua University, Beijing 100084, China.
Science. 2012 Feb 10;335(6069):720-3. doi: 10.1126/science.1215670. Epub 2012 Jan 5.
TAL (transcription activator-like) effectors, secreted by phytopathogenic bacteria, recognize host DNA sequences through a central domain of tandem repeats. Each repeat comprises 33 to 35 conserved amino acids and targets a specific base pair by using two hypervariable residues [known as repeat variable diresidues (RVDs)] at positions 12 and 13. Here, we report the crystal structures of an 11.5-repeat TAL effector in both DNA-free and DNA-bound states. Each TAL repeat comprises two helices connected by a short RVD-containing loop. The 11.5 repeats form a right-handed, superhelical structure that tracks along the sense strand of DNA duplex, with RVDs contacting the major groove. The 12th residue stabilizes the RVD loop, whereas the 13th residue makes a base-specific contact. Understanding DNA recognition by TAL effectors may facilitate rational design of DNA-binding proteins with biotechnological applications.
TAL（转录激活样）效应子，由植物病原菌分泌，通过串联重复的中央结构域识别宿主 DNA 序列。每个重复由 33 到 35 个保守氨基酸组成，通过位于第 12 位和第 13 位的两个超变残基[称为重复可变二肽残基（RVD）]，针对特定的碱基对。在此，我们报告了处于无 DNA 和 DNA 结合状态的 11.5 个重复 TAL 效应子的晶体结构。每个 TAL 重复由两个通过含有 RVD 的短环连接的螺旋组成。11.5 个重复形成右手超螺旋结构，沿着 DNA 双链的有义链追踪，RVD 与主沟接触。第 12 位残基稳定 RVD 环，而第 13 位残基则与碱基特异性接触。理解 TAL 效应子的 DNA 识别可能有助于合理设计具有生物技术应用的 DNA 结合蛋白。
