Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
Biological and Biomedical Sciences Program, Harvard University, Cambridge, MA, USA.
Science. 2021 Oct 29;374(6567):580-585. doi: 10.1126/science.abi9009. Epub 2021 Sep 23.
ATP-binding cassette (ABC) transporters couple adenosine 5′-triphosphate (ATP) hydrolysis to substrate transport across biological membranes. Although many are promising drug targets, their mechanisms of modulation by small-molecule inhibitors remain largely unknown. Two first-generation inhibitors of the MsbA transporter, tetrahydrobenzothiophene 1 (TBT1) and G247, induce opposite effects on ATP hydrolysis. Using single-particle cryo–electron microscopy and functional assays, we show that TBT1 and G247 bind adjacent yet separate pockets in the MsbA transmembrane domains. Two TBT1 molecules asymmetrically occupy the substrate-binding site, which leads to a collapsed inward-facing conformation with decreased distance between the nucleotide-binding domains (NBDs). By contrast, two G247 molecules symmetrically increase NBD distance in a wide inward-open state of MsbA. The divergent mechanisms of action of these MsbA inhibitors provide important insights into ABC transporter pharmacology.
三磷酸腺苷结合盒（ABC）转运蛋白将三磷酸腺苷（ATP）水解与生物膜上的底物运输偶联。尽管许多都是有前途的药物靶点，但它们被小分子抑制剂调节的机制在很大程度上仍不清楚。MsbA 转运蛋白的两种第一代抑制剂四氢苯并噻吩 1（TBT1）和 G247 对 ATP 水解产生相反的影响。我们使用单颗粒冷冻电镜和功能测定表明，TBT1 和 G247 结合 MsbA 跨膜域中相邻但分开的口袋。两个 TBT1 分子不对称地占据底物结合位点，导致核苷酸结合结构域（NBD）之间的距离减小，向内折叠构象塌陷。相比之下，两个 G247 分子在 MsbA 的宽向内开放状态下对称地增加 NBD 距离。这些 MsbA 抑制剂的不同作用机制为 ABC 转运蛋白药理学提供了重要的见解。
