Institute for Biophysical Chemistry and Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt, Max von Laue Str. 9, 60438, Frankfurt, Germany.
Commun Biol. 2024 Jan 5;7(1):43. doi: 10.1038/s42003-023-05617-0.
The ABC transporter MsbA plays a critical role in Gram-negative bacteria in the regulation of the outer membrane by translocating core-LPS across the inner membrane. Additionally, a broad substrate specificity for lipophilic drugs has been shown. The allosteric interplay between substrate binding in the transmembrane domains and ATP binding and turnover in the nucleotide-binding domains must be mediated via the NBD/TMD interface. Previous studies suggested the involvement of two intracellular loops called coupling helix 1 and 2 (CH1, CH2). Here, we demonstrate by solid-state NMR spectroscopy that substantial chemical shift changes within both CH1 and CH2 occur upon substrate binding, in the ATP hydrolysis transition state, and upon inhibitor binding. CH2 is domain-swapped within the MsbA structure, and it is noteworthy that substrate binding induces a larger response in CH2 compared to CH1. Our data demonstrate that CH1 and CH2 undergo structural changes as part of the TMD-NBD cross-talk.
ABC 转运蛋白 MsbA 在革兰氏阴性菌中通过将核心 LPS 穿过内膜转运来调节外膜，起着关键作用。此外，还表现出对亲脂性药物的广泛底物特异性。底物结合在跨膜结构域和 ATP 结合与核苷酸结合结构域的水解转换状态之间的变构相互作用必须通过 NBD/TMD 界面来介导。先前的研究表明两个细胞内环（称为偶联螺旋 1 和 2，CH1 和 CH2）的参与。在这里，我们通过固态 NMR 光谱证明，在底物结合、ATP 水解过渡态和抑制剂结合时，CH1 和 CH2 内都发生了明显的化学位移变化。CH2 在 MsbA 结构内发生结构交换，值得注意的是，与 CH1 相比，底物结合诱导 CH2 发生更大的响应。我们的数据表明，CH1 和 CH2 作为 TMD-NBD 交叉对话的一部分发生结构变化。
