Colleau M, Hervé P, Fellmann P, Devaux P F
Institut de Biologie Physico-Chimique (UA 526 CNRS), Paris, France.
Chem Phys Lipids. 1991 Jan-Feb;57(1):29-37. doi: 10.1016/0009-3084(91)90046-e.
The outside-inside passage and transmembrane equilibrium distribution of several amphiphilic fluorescent phospholipids were examined in human erythrocytes. The results were compared with previous kinetic data obtained with spin-labeled phospholipids and with the equilibrium distribution of endogenous lipids in erythrocytes. When a nitro benzoxadiazole (NBD) was at the terminal position of a 6 carbon beta-chain, the outside-inside diffusion of the fluorescent phosphatidylserine (PS) analogue was slower, and the plateau lower than with long chain radioactive PS or spin-labeled PS. The corresponding phosphatidylethanolamine (PE) did not flip nor did the phosphatidylcholine (PC) analogue. With a NBD at the 12th carbon of a 18C alpha-chain, the amino-derivatives behaved more like endogenous PS and PE, i.e. they accumulated rapidly on the inner monolayer; however, the phosphatidylcholine analogue reached a plateau corresponding to 50% inside within 2 h at 37 degrees C, indicative of an abnormal rapid diffusion. In the latter case, changing the beta-chain from four to eight carbons had no influence on this rapid diffusion. We conclude that when the NBD is close to the glycerol moiety, it diminishes the affinity of the aminophospholipids for the aminophospholipid translocase. When it is close to the methyl terminal of an acyl chain, there is an acceleration of the spontaneous flip-flop. Presumably the polarity of the NBD is responsible for an unconventional orientation of the flexible acyl chain, thereby causing the transmembrane destabilization of the phospholipid. Overall these results illustrate the respective roles of spontaneous diffusion and translocase activity on transmembrane equilibrium distribution of phospholipids. They also show that NBD derivatives should be used cautiously as indicators of endogenous phospholipids.
在人红细胞中检测了几种两亲性荧光磷脂的外-内通道和跨膜平衡分布。将结果与先前用自旋标记磷脂获得的动力学数据以及红细胞内源性脂质的平衡分布进行了比较。当硝基苯并恶二唑（NBD）位于6碳β链的末端位置时，荧光磷脂酰丝氨酸（PS）类似物的外-内扩散较慢，且平台期低于长链放射性PS或自旋标记PS。相应的磷脂酰乙醇胺（PE）没有翻转，磷脂酰胆碱（PC）类似物也没有。当NBD位于18碳α链的第12个碳原子处时，氨基衍生物的行为更类似于内源性PS和PE，即它们在内侧单层迅速积累；然而，磷脂酰胆碱类似物在37℃下2小时内达到了对应于50%在内侧的平台期，表明存在异常快速的扩散。在后一种情况下，将β链从四个碳原子改为八个碳原子对这种快速扩散没有影响。我们得出结论，当NBD靠近甘油部分时，它会降低氨基磷脂对氨基磷脂转位酶的亲和力。当它靠近酰基链的甲基末端时，自发翻转会加速。推测NBD的极性导致了柔性酰基链的非常规取向，从而导致磷脂的跨膜不稳定。总体而言，这些结果说明了自发扩散和转位酶活性在磷脂跨膜平衡分布中的各自作用。它们还表明，NBD衍生物作为内源性磷脂的指示剂应谨慎使用。
