Helmkamp G M
Biochim Biophys Acta. 1980 Jan 25;595(2):222-34. doi: 10.1016/0005-2736(80)90085-1.
The major phospholipid exchange protein from bovine brain catalyzes the transfer of phosphatidylinositol and phosphatidylcholine between rat liver microsomes and sonicated liposomes. The effect of liposomal lipid composition on the transfer of these phospholipids has been investigated. Standard liposomes contained phosphatidylcholine-phosphatidic acid (98 : 2, mol%); in general, phosphatidylcholine was substituted by various positively charged, negatively charged, or zwitterionic lipids. The transfer of phosphatidylinositol was essentially unaffected by the incorporation into liposomes of phosphatidic acid, phosphatidylserine, or phosphatidylglycerol (5--20 mol%) but strongly depressed by the incorporation of stearylamine (10--40 mol%). Marked stimulation (2--4-fold) of transfer activity was observed into liposomes containing phosphatidylethanolamine (2--40 mol%). The inclusion of sphingomyelin in the acceptor liposomes gave mixed results: stimulation at low levels (2--10 mol%) and inhibition at higher levels (up to 40 mol%). Cholesterol slightly diminished transfer activity at a liposome cholesterol/phospholipid molar ratio of 0.81. Similar effects were noted for the transfer to phospholipidcholine from microsomes to these various liposomes. Compared to standard liposomes, the magnitude of Km tended to increase for liposomes which depressed phospholipid transfer and to decrease for those which stimulated; little change was observed in the values of V. Single phospholipid liposomes of phosphatidylinositol were inhibitory when added to standard liposomes. Because bovine brain phospholipid exchange protein is able to distinguish among a wide spectrum of membrane interfaces, taking into account variations in the polar head groups as well as the fatty acyl moieties of the liposomal phospholipids, it may be considered a reasonable model system for protein-lipid and protein-membrane interactions.
来自牛脑的主要磷脂交换蛋白催化磷脂酰肌醇和磷脂酰胆碱在大鼠肝微粒体和超声处理的脂质体之间的转移。已研究了脂质体脂质组成对这些磷脂转移的影响。标准脂质体含有磷脂酰胆碱 - 磷脂酸（98∶2，摩尔％）；一般而言，磷脂酰胆碱被各种带正电荷、带负电荷或两性离子脂质所取代。磷脂酰肌醇的转移基本上不受脂质体中掺入磷脂酸、磷脂丝氨酸或磷脂甘油（5 - 20摩尔％）的影响，但掺入硬脂胺（10 - 40摩尔％）会使其强烈降低。在含有磷脂酰乙醇胺（2 - 40摩尔％）的脂质体中观察到转移活性有明显刺激（2 - 4倍）。受体脂质体中包含鞘磷脂产生了混合结果：低水平（2 - 10摩尔％）时有刺激作用，而高水平（高达40摩尔％）时则有抑制作用。当脂质体胆固醇/磷脂摩尔比为0.81时，胆固醇会稍微降低转移活性。从微粒体向这些各种脂质体转移磷脂酰胆碱时也观察到类似的效果。与标准脂质体相比，对于抑制磷脂转移的脂质体，Km值往往会增加，而对于刺激磷脂转移的脂质体，Km值则会降低；V值变化不大。当将磷脂酰肌醇的单一磷脂脂质体添加到标准脂质体中时具有抑制作用。由于牛脑磷脂交换蛋白能够区分广泛的膜界面，同时考虑到脂质体磷脂的极性头部基团以及脂肪酰基部分的变化，它可被视为蛋白质 - 脂质和蛋白质 - 膜相互作用的合理模型系统。
