Abstract：
Cardiolipin (CL) has been shown to play a crucial role in regulating the function of proteins in the inner mitochondrial membrane. As the most abundant protein of the inner mitochondrial membrane, the ADP/ATP carrier (AAC) has long been the model of choice to study CL-protein interactions, and specifically bound CLs have been identified in a variety of crystal structures of AAC. However, how CL binding affects the structural dynamics of AAC in atomic detail remains largely elusive. Here we compared all-atom molecular dynamics simulations on bovine AAC1 in lipid bilayers with and without CLs. Our results show that on the current microsecond simulation time scale: 1) CL binding does not significantly affect overall stability of the carrier or structural symmetry at the matrix-gate level; 2) pocket volumes of the carrier and interactions involved in the matrix-gate network become more heterogeneous in parallel simulations with membranes containing CLs; 3) CL binding consistently strengthens backbone hydrogen bonds within helix H2 near the matrix side; and 4) CLs play a consistent stabilizing role on the domain 1-2 interface through binding with the R30:R71:R151 stacking structure and fixing the M2 loop in a defined conformation. CL is necessary for the formation of this stacking structure, and this structure in turn forms a very stable CL binding site. Such a delicate equilibrium suggests the strictly conserved R30:R71:R151stacking structure of AACs could function as a switch under regulation of CLs. Taken together, these results shed new light on the CL-mediated modulation of AAC function.
摘要：
心磷脂（CL）已被证明在调节线粒体内膜中蛋白质的功能中起关键作用。作为线粒体内膜中最丰富的蛋白质，ADP/ATP载体（AAC）长期以来一直是研究CL-蛋白质相互作用的首选模型，和特异性结合的CL已经在AAC的各种晶体结构中被鉴定。然而,CL结合如何影响原子细节中AAC的结构动力学仍然很难理解。在这里，我们比较了有和没有CLs的脂质双层中牛AAC1的全原子分子动力学模拟。我们的结果表明，在当前的微秒模拟时间尺度上：1）CL结合不会显着影响载体的整体稳定性或在基质-门水平上的结构对称性；2）载体的口袋体积和参与基质-门网络的相互作用在含有CL的膜的平行模拟中变得更加异质；3）CL结合一致地加强了在基质侧附近的螺旋H2内的主链氢键；和4）CLs在域1-2上发挥一致的稳定作用通过CL是形成这种堆叠结构所必需的，并且该结构又形成非常稳定的CL结合位点。这种微妙的平衡表明AAC的严格保守的R30：R71：R151堆叠结构可以在CLs的调节下充当开关。一起来看,这些结果为CL介导的AAC功能调节提供了新的思路。
