Department of Chemistry, Chicago Center for Theoretical Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois.
Department of Biochemistry, University of Oxford, Oxford, UK.
Biophys J. 2022 Jun 21;121(12):2266-2278. doi: 10.1016/j.bpj.2022.05.029. Epub 2022 May 25.
Proton-coupled peptide transporters (POTs) are crucial for the uptake of di- and tripeptides as well as drug and prodrug molecules in prokaryotes and eukaryotic cells. We illustrate from multiscale modeling how transmembrane proton flux couples within a POT protein to drive essential steps of the full functional cycle: 1) protonation of a glutamate on transmembrane helix 7 (TM7) opens the extracellular gate, allowing ligand entry; 2) inward proton flow induces the cytosolic release of ligand by varying the protonation state of a second conserved glutamate on TM10; 3) proton movement between TM7 and TM10 is thermodynamically driven and kinetically permissible via water proton shuttling without the participation of ligand. Our results, for the first time, give direct computational confirmation for the alternating access model of POTs, and point to a quantitative multiscale kinetic picture of the functioning protein mechanism.
质子偶联肽转运蛋白（POTs）对于原核生物和真核细胞中二肽和三肽以及药物和前药分子的摄取至关重要。我们通过多尺度建模来说明，在 POT 蛋白内，跨膜质子流如何偶联以驱动完整功能循环的基本步骤：1）跨膜螺旋 7（TM7）上的谷氨酸质子化打开细胞外门，允许配体进入；2）质子内流通过改变 TM10 上第二个保守谷氨酸的质子化状态诱导细胞溶质中配体的释放；3）质子在 TM7 和 TM10 之间的运动是热力学驱动的，并且通过水质子穿梭在没有配体参与的情况下在动力学上是可行的。我们的结果首次为 POT 的交替访问模型提供了直接的计算证实，并指出了功能蛋白机制的定量多尺度动力学图景。
