Machida K, Ohnishi S I
Biochim Biophys Acta. 1980 Feb 28;596(2):201-9. doi: 10.1016/0005-2736(80)90355-7.
Effect of bilayer membrane curvature of substrate phosphatidylcholine and inhibitor phosphatidylserine on the activity of phosphatidylcholine exchange protein has been studied by measuring transfer of spin-labeled phosphatidylcholine between vesicles, vesicles and liposomes, and between liposomes. The transfer rate between vesicles was more than 100 times larger than that between vesicles and liposomes. The transfer rate between liposomes was still smaller than that between vesicles and liposomes and nearly the same as that in the absence of exchange protein. The markedly enhanced exchange with vesicles was ascribed to the asymmetric packing of phospholipid molecules in the outer layer of the highly curved bilayer membrane. The inhibitory effect of phosphatidylserine was also greatly dependent on the membrane curvature. The vesicles with diameter of 17 nm showed more than 20 times larger inhibitory activity than those with diameter of 22 nm. The inhibitory effect of liposomes was very small. The size dependence was ascribed to stronger binding of the exchange protein to membranes with higher curvatures. The protein-mediated transfer from vesicles to spiculated erythrocyte ghosts was about four times faster than that to cup-shaped ghosts. This was ascribed to enhanced transfer to the highly curved spiculated membrane sites rather than greater mobility of phosphatidylcholine in the spiculated ghost membrane.
通过测量自旋标记的磷脂酰胆碱在囊泡之间、囊泡与脂质体之间以及脂质体之间的转移，研究了底物磷脂酰胆碱和抑制剂磷脂酰丝氨酸的双层膜曲率对磷脂酰胆碱交换蛋白活性的影响。囊泡之间的转移速率比囊泡与脂质体之间的转移速率大100倍以上。脂质体之间的转移速率仍小于囊泡与脂质体之间的转移速率，且与不存在交换蛋白时的转移速率几乎相同。与囊泡的交换显著增强归因于磷脂分子在高度弯曲的双层膜外层中的不对称堆积。磷脂酰丝氨酸的抑制作用也很大程度上取决于膜曲率。直径为17 nm的囊泡的抑制活性比直径为22 nm的囊泡大20倍以上。脂质体的抑制作用非常小。尺寸依赖性归因于交换蛋白与曲率较高的膜的更强结合。蛋白介导的从囊泡到有刺红细胞血影的转移比到杯状血影的转移快约四倍。这归因于向高度弯曲的有刺膜位点的转移增强，而不是磷脂酰胆碱在有刺血影膜中的更大流动性。
