Curvature-Dependent Binding of Cytochrome c to Cardiolipin
Curvature-Dependent Binding of Cytochrome c to Cardiolipin
复制标题
DOI：
10.1021/jacs.0c07301
复制
发表时间：
2020-11-18
影响因子：
15
通讯作者：
Bowler, Bruce E.
中科院分区：
文献类型：
--
作者：
Elmer-Dixon, Margaret M.;Xie, Ziqing;Bowler, Bruce E.
细胞色素c在氧化脂质和启动凋亡途径之前，在线粒体内膜的凹面上结合心磷脂。这种相互作用已经在体外进行了研究，其中模拟结合环境的膜曲率是困难的。在这里，我们报告结合到凹，心磷脂，膜表面和比较结果凸结合在相同的条件下。对于结合到含有心磷脂的囊泡的凸形外表面，观察到两步结构重排，其中在暴露的脂质与蛋白质的比率（LPR）接近10处发生通过Soret圆二色性（CD）可检测的小重排，并且在暴露的LPR接近23处发生通过Trp 59荧光可检测的部分解折叠。在含心磷脂囊泡的凹内表面上，由Soret CD和Trp 59荧光监测的结构转变是一致的，并且发生在接近58的暴露LPR处。在线粒体嵴的凹内表面，我们估计心磷脂对细胞色素c的LPR在50和100之间。因此，细胞色素c可能已经适应了它的天然环境，使它可以经历一个构象变化，开关其过氧化物酶活性时，它结合到CL-含膜的嵴细胞凋亡早期。我们的研究结果表明，膜曲率定性影响外周蛋白质-脂质相互作用，也突出了在体外结合研究和他们的生理对应物，如心磷脂，涉及之间的差距。
Cytochrome c binds cardiolipin on the concave surface of the inner mitochondrial membrane, before oxidizing the lipid and initiating the apoptotic pathway. This interaction has been studied in vitro, where mimicking the membrane curvature of the binding environment is difficult. Here we report binding to concave, cardiolipin-containing, membrane surfaces and compare findings to convex binding under the same conditions. For binding to the convex outer surface of cardiolipin-containing vesicles, a two-step structural rearrangement is observed with a small rearrangement detectable by Soret circular dichroism (CD) occurring at an exposed lipid-to-protein ratio (LPR) near 10 and partial unfolding detectable by Trp59 fluorescence occurring at an exposed LPR near 23. On the concave inner surface of cardiolipin-containing vesicles, the structural transitions monitored by Soret CD and Trp59 fluorescence are coincident and occur at an exposed LPR near 58. On the concave inner surface of mitochondrial cristae, we estimate the LPR of cardiolipin to cytochrome c is between 50 and 100. Thus, cytochrome c may have adapted to its native environment so that it can undergo a conformational change that switches on its peroxidase activity when it binds to CL-containing membranes in the cristae early in apoptosis. Our results show that membrane curvature qualitatively affects peripheral protein-lipid interactions and also highlights the disparity between in vitro binding studies and their physiological counterparts where cone-shaped lipids, like cardiolipin, are involved.