Laboratory of Membrane Biophysics and Biology, The Rockefeller University, New York, NY, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA.
Laboratory of Membrane Biophysics and Biology, The Rockefeller University, New York, NY, USA; Tri-Institutional Training Program in Chemical Biology, The Rockefeller University, New York, NY, USA.
Cell. 2017 Jul 27;170(3):483-491.e8. doi: 10.1016/j.cell.2017.06.041. Epub 2017 Jul 20.
The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel evolved from an ATP-binding cassette transporter. CFTR channel gating is strictly coupled to phosphorylation and ATP hydrolysis. Previously, we reported essentially identical structures of zebrafish and human CFTR in the dephosphorylated, ATP-free form. Here, we present the structure of zebrafish CFTR in the phosphorylated, ATP-bound conformation, determined by cryoelectron microscopy to 3.4 Å resolution. Comparison of the two conformations shows major structural rearrangements leading to channel opening. The phosphorylated regulatory domain is disengaged from its inhibitory position; the nucleotide-binding domains (NBDs) form a "head-to-tail" dimer upon binding ATP; and the cytoplasmic pathway, found closed off in other ATP-binding cassette transporters, is cracked open, consistent with CFTR's unique channel function. Unexpectedly, the extracellular mouth of the ion pore remains closed, indicating that local movements of the transmembrane helices can control ion access to the pore even in the NBD-dimerized conformation.
囊性纤维化跨膜电导调节因子（CFTR）是一种阴离子通道，由 ATP 结合盒转运蛋白进化而来。CFTR 通道门控严格偶联于磷酸化和 ATP 水解。此前，我们报道了去磷酸化、无 ATP 形式的斑马鱼和人 CFTR 的基本相同结构。在此，我们通过冷冻电镜以 3.4Å 的分辨率确定了磷酸化、ATP 结合的斑马鱼 CFTR 结构。两种构象的比较表明，主要的结构重排导致通道开放。磷酸化的调节域与抑制位置脱开；核苷酸结合域（NBD）在结合 ATP 后形成“头对头”二聚体；细胞质途径在其他 ATP 结合盒转运蛋白中被封闭，现在被打开，这与 CFTR 独特的通道功能一致。出乎意料的是，离子通道的细胞外口仍然关闭，这表明跨膜螺旋的局部运动即使在 NBD 二聚化构象中也可以控制离子进入孔道。
