Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA.
Division of Biostatistics, University of Minnesota, Minneapolis, MN, USA.
Sci Rep. 2022 May 10;12(1):7676. doi: 10.1038/s41598-022-11221-9.
BAR (Bin/Amphiphysin/Rvs) domain containing proteins function as lipid bilayer benders and curvature sensors, and they contribute to membrane shaping involved in cell signaling and metabolism. The mechanism for their membrane shape sensing has been investigated by both equilibrium binding and kinetic studies. In prior research, stopped-flow spectroscopy has been used to deduce a positive dependence on membrane curvature for the binding rate constant, k, of a BAR protein called endophilin. However, the impact of bulk diffusion of endophilin, on the kinetic binding parameters has not been thoroughly considered. Employing similar methods, and using lipid vesicles of multiple sizes, we obtained a linear dependence of k on vesicle curvature. However, we found that the observed relation can be explained without considering the local curvature sensing ability of endophilin in the membrane association process. In contrast, the diffusion-independent unbinding rate constant (k) obtained from stopped-flow measurements shows a negative dependence on membrane curvature, which is controlled/mediated by endophilin-membrane interactions. This latter dependency, in addition to protein-protein interactions on the membrane, explains the selective binding of BAR proteins to highly curved membranes in equilibrium binding experiments.
BAR（Bin/Amphiphysin/Rvs）结构域包含蛋白作为脂质双层弯曲蛋白和曲率传感器发挥作用，它们有助于细胞信号转导和代谢过程中涉及的膜重塑。通过平衡结合和动力学研究已经研究了它们的膜形状感应机制。在先前的研究中，使用停流光谱学推断出一种 BAR 蛋白（称为内收蛋白）的结合速率常数 k 与膜曲率呈正相关。然而，内收蛋白的体相扩散对动力学结合参数的影响尚未得到充分考虑。我们采用类似的方法，并使用多种大小的脂质囊泡，得到了 k 与囊泡曲率的线性关系。然而，我们发现，无需考虑内收蛋白在膜缔合过程中的局部曲率感应能力，就可以解释所观察到的关系。相比之下，从停流测量中获得的扩散独立的解吸速率常数（k）与膜曲率呈负相关，这由内收蛋白-膜相互作用控制/介导。这种依赖性，除了膜上的蛋白质-蛋白质相互作用外，还解释了 BAR 蛋白在平衡结合实验中对高度弯曲的膜的选择性结合。
