National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 100101, Beijing, China.
School of Life Sciences, University of Chinese Academy of Sciences, 100049, Beijing, China.
Commun Biol. 2020 Aug 25;3(1):468. doi: 10.1038/s42003-020-01121-x.
Cardiolipin, an essential mitochondrial physiological regulator, is synthesized from phosphatidic acid (PA) in the inner mitochondrial membrane (IMM). PA is synthesized in the endoplasmic reticulum and transferred to the IMM via the outer mitochondrial membrane (OMM) under mediation by the Ups1/Mdm35 protein family. Despite the availability of numerous crystal structures, the detailed mechanism underlying PA transfer between mitochondrial membranes remains unclear. Here, a model of Ups1/Mdm35-membrane interaction is established using combined crystallographic data, all-atom molecular dynamics simulations, extensive structural comparisons, and biophysical assays. The α2-loop, L2-loop, and α3 helix of Ups1 mediate membrane interactions. Moreover, non-complexed Ups1 on membranes is found to be a key transition state for PA transfer. The membrane-bound non-complexed Ups1/ membrane-bound Ups1 ratio, which can be regulated by environmental pH, is inversely correlated with the PA transfer activity of Ups1/Mdm35. These results demonstrate a new model of the fine conformational changes of Ups1/Mdm35 during PA transfer.
心磷脂是一种重要的线粒体生理调节剂，它由线粒体内膜（IMM）中的磷酸酸（PA）合成。PA 在内质网中合成，并在外膜（OMM）的介导下通过线粒体外膜（OMM）转移到 IMM。尽管有许多晶体结构，但 PA 在线粒体膜之间转移的详细机制仍不清楚。本研究利用晶体学数据、全原子分子动力学模拟、广泛的结构比较和生物物理测定，建立了 Ups1/Mdm35-膜相互作用的模型。Ups1 的α2-环、L2-环和α3 螺旋介导膜相互作用。此外，还发现非复合物 Ups1 是 PA 转移的关键过渡态。可以通过环境 pH 值调节的膜结合非复合物 Ups1/膜结合 Ups1 比值与 Ups1/Mdm35 的 PA 转移活性呈负相关。这些结果表明了 Ups1/Mdm35 在 PA 转移过程中精细构象变化的新模型。
