Holdsworth G, Noel J G, Stedje K, Shinomiya M, Jackson R L
Biochim Biophys Acta. 1984 Jul 26;794(3):472-8. doi: 10.1016/0005-2760(84)90014-6.
Apolipoprotein C-II, the activator protein of lipoprotein lipase, contains 78 amino acids with a single residue of arginine at position 49. Chemical modification of apolipoprotein C-II with 1,2-cyclohexanedione or 2,3-butanedione results in a loss of both the arginine residue and the ability of the protein to enhance the activity of bovine milk lipoprotein lipase toward a trioleoylglycerol substrate; removal of the modifying group restores arginine and more than 70% of the activating property of the apolipoprotein. Arginine modification of apolipoprotein C-II does not effect its lipid-binding properties as assessed by its association to sonicated vesicles of dimyristoylphosphatidylcholine. Furthermore, secondary structure associated with complex formation with dimyristoylphosphatidylcholine are nearly identical for the unmodified, 1,2-cyclohexanedione-modified or modified-reversed proteins. These results suggest that arginine-49 of apolipoprotein C-II is situated at or near an amino acid sequence domain involved in the activation of lipoprotein lipase. However, a guanidinium group is not required for lipid binding.
载脂蛋白C-II是脂蛋白脂肪酶的激活蛋白，含有78个氨基酸，在第49位有一个精氨酸残基。用1,2-环己二酮或2,3-丁二酮对载脂蛋白C-II进行化学修饰，会导致精氨酸残基丢失，且该蛋白增强牛乳脂蛋白脂肪酶对三油酰甘油底物活性的能力丧失；去除修饰基团可使精氨酸恢复，并使载脂蛋白的激活特性恢复70%以上。通过载脂蛋白C-II与二肉豆蔻酰磷脂酰胆碱超声处理囊泡的结合评估发现，精氨酸修饰不会影响其脂质结合特性。此外，未修饰、1,2-环己二酮修饰或修饰后逆转的蛋白质与二肉豆蔻酰磷脂酰胆碱形成复合物时的二级结构几乎相同。这些结果表明，载脂蛋白C-II的第49位精氨酸位于参与脂蛋白脂肪酶激活的氨基酸序列结构域处或附近。然而，脂质结合不需要胍基。
