Smith L M, Rubenstein J L, Parce J W, McConnell H M
Biochemistry. 1980 Dec 9;19(25):5907-11. doi: 10.1021/bi00566a037.
The translational diffusion of fluorescent-labeled M-13 phage coat protein (FITC-M-13), an integral membrane protein, has been measured in mixtures of phosphatidylcholines and cholesterol, using a pattern photobleaching technique. At temperatures below the chain-melting transition temperature of dimyristoylphosphatidylcholine (DMPC) (23.8 degrees C), the lateral diffusion coefficient of M-13 shows a marked increase when the cholesterol concentration is increased above 20 mol %. A similar marked increase in the lateral diffusion coefficient of a fluorescent phospholipid is also observed. At temperatures above the chain-melting transition temperature of DMPC, a minimum is observed in the lateral diffusion coefficient of FITC-M-13 for cholesterol concentrations in the vicinity of 25 mol %. This minimum in the diffusion coefficient of FITC-M-13 is also observed at 25 mol % cholesterol in egg phosphatidylcholine at 15 degrees C. No such minimum is observed for the lateral diffusion coefficient of the fluorescent lipid. The lateral diffusion coefficient of FITC-M-13 is large (greater than 10(-9) cm2/s) at all cholesterol concentrations for temperatures above the chain-melting transition temperature of the phosphatidylcholine. Several other proteins contain hydrophobic regions similar to that of the M-13 coat protein. We anticipate that a number of proteins of this type will show similar diffusional behavior, in particular exhibiting rapid diffusion throughout a wide range of lipid composition.
利用图案光漂白技术，在磷脂酰胆碱和胆固醇的混合物中测量了荧光标记的M - 13噬菌体外壳蛋白（FITC - M - 13，一种整合膜蛋白）的平移扩散。在低于二肉豆蔻酰磷脂酰胆碱（DMPC）的链熔化转变温度（23.8摄氏度）时，当胆固醇浓度增加到20摩尔％以上时，M - 13的横向扩散系数显著增加。在荧光磷脂的横向扩散系数中也观察到类似的显著增加。在高于DMPC的链熔化转变温度时，对于胆固醇浓度在25摩尔％附近的情况，观察到FITC - M - 13的横向扩散系数出现最小值。在15摄氏度下，在鸡蛋磷脂酰胆碱中胆固醇含量为25摩尔％时，也观察到FITC - M - 13扩散系数的这种最小值。对于荧光脂质的横向扩散系数未观察到这种最小值。对于高于磷脂酰胆碱链熔化转变温度的温度，在所有胆固醇浓度下，FITC - M - 13的横向扩散系数都很大（大于10^(-9) cm²/s）。其他几种蛋白质含有与M - 13外壳蛋白类似的疏水区域。我们预计许多这种类型的蛋白质将表现出类似的扩散行为，特别是在广泛的脂质组成范围内表现出快速扩散。
