Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, A3-025 Seattle, WA 98019, USA.
Science. 2012 Feb 10;335(6069):716-9. doi: 10.1126/science.1216211. Epub 2012 Jan 5.
DNA recognition by TAL effectors is mediated by tandem repeats, each 33 to 35 residues in length, that specify nucleotides via unique repeat-variable diresidues (RVDs). The crystal structure of PthXo1 bound to its DNA target was determined by high-throughput computational structure prediction and validated by heavy-atom derivatization. Each repeat forms a left-handed, two-helix bundle that presents an RVD-containing loop to the DNA. The repeats self-associate to form a right-handed superhelix wrapped around the DNA major groove. The first RVD residue forms a stabilizing contact with the protein backbone, while the second makes a base-specific contact to the DNA sense strand. Two degenerate amino-terminal repeats also interact with the DNA. Containing several RVDs and noncanonical associations, the structure illustrates the basis of TAL effector-DNA recognition.
TAL 效应物通过串联重复序列识别 DNA，每个重复序列长 33 到 35 个残基，通过独特的重复可变双残基 (RVD) 来指定核苷酸。通过高通量计算结构预测确定了 PthXo1 与其 DNA 靶标的晶体结构，并通过重原子衍生化进行了验证。每个重复形成一个左手的双螺旋束，向 DNA 呈现一个含有 RVD 的环。重复序列自我缔合形成一个右手超螺旋，包裹在 DNA 的大沟上。第一个 RVD 残基与蛋白质骨架形成稳定的接触，而第二个 RVD 残基与 DNA 的有义链形成碱基特异性接触。两个简并的氨基末端重复序列也与 DNA 相互作用。该结构包含几个 RVD 和非典型的相互作用，说明了 TAL 效应物-DNA 识别的基础。
