Shinagawa K, Ohya M, Higashijima T, Wakamatsu K
Department of Biochemical Sciences, Faculty of Engineering, Gunma University.
J Biochem. 1994 Mar;115(3):463-8. doi: 10.1093/oxfordjournals.jbchem.a124360.
We previously showed that peptides corresponding to the N-terminal parts of the third intracellular loops of turkey and hamster beta-adrenergic receptors (tu beta I3N and ha beta I3N, respectively) can activate the GS protein (one of the GTP-binding regulatory proteins which couples to the beta-adrenergic receptor) reconstituted in phospholipid vesicles, and also that such activation can be greatly enhanced by a modification which increases the hydrophobicity of the peptides. These observed phenomena suggest that the interaction with phospholipid membranes is important for the activity of these peptides; hence, in the present study we employed circular dichroism to analyze the interaction of the synthetic peptides corresponding to the intracellular loops of G protein-coupled receptors with phosphatidylserine/phosphatidylcholine mixed vesicles. The tu beta I3N and ha beta I3N peptides were subsequently found to take on an alpha-helical conformation upon binding with the vesicles, whereas those corresponding to the intracellular loops of m1 and m2 muscarinic acetylcholine receptors in contrast did not interact with the vesicles. The positions of several side chains of the membrane-bound loop peptides were also determined. Our results show for the first time the interaction occurring between the intracellular loops of beta-adrenergic receptors and a phospholipid membrane.
我们之前表明，对应于火鸡和仓鼠β-肾上腺素能受体第三细胞内环N端部分的肽段（分别为tuβI3N和haβI3N）能够激活重构于磷脂囊泡中的GS蛋白（一种与β-肾上腺素能受体偶联的GTP结合调节蛋白），并且还表明，通过增加肽段疏水性的修饰可极大增强这种激活作用。这些观察到的现象表明，与磷脂膜的相互作用对这些肽段的活性很重要；因此，在本研究中，我们采用圆二色性来分析对应于G蛋白偶联受体细胞内环的合成肽段与磷脂酰丝氨酸/磷脂酰胆碱混合囊泡的相互作用。随后发现，tuβI3N和haβI3N肽段与囊泡结合后呈现α-螺旋构象，而对应于毒蕈碱型乙酰胆碱受体m1和m2细胞内环的肽段则相反，不与囊泡相互作用。还确定了膜结合环肽段几个侧链的位置。我们的结果首次展示了β-肾上腺素能受体细胞内环与磷脂膜之间发生的相互作用。
