Gustafsson M, Vandenbussche G, Curstedt T, Ruysschaert J M, Johansson J
Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
FEBS Lett. 1996 Apr 15;384(2):185-8. doi: 10.1016/0014-5793(96)00290-6.
The 21-residue peptide KLLLLKLLLLKLLLLKLLLLK (KL4) has been synthesized and analyzed regarding its secondary structure and orientation in lipid environments. Fourier transform infrared and circular dichroism spectroscopy shows that the peptide exhibits approximately 80% alpha-helical content both in dodecylphosphocholine micelles and in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)/phosphatidylglycerol (PG) 7:3 (w/w) bilayers. The positively charged lysine residues are evenly distributed over the entire, otherwise nonpolar, circumference of the helix. This is in sharp contrast to the uneven distribution of polar and nonpolar residues in amphipathic helices. Fourier transform infrared spectroscopy of the peptide inserted in DPPC/PG bilayers shows that the helical axis is oriented parallel to the lipid acyl chains. These data do not support a previous hypothesis that the KL4 peptide interacts with peripheral parts of a phospholipid monolayer and mimics the pulmonary surfactant protein SP-B, which is composed of several amphipathic alpha-helices. KL4 accelerates the spreading of phospholipid mixtures at an air/water interface but does so less efficiently than other transmembranous helical polypeptides studied.
已合成了由21个氨基酸残基组成的肽KLLLLKLLLLKLLLLKLLLLK（KL4），并对其在脂质环境中的二级结构和取向进行了分析。傅里叶变换红外光谱和圆二色光谱表明，该肽在十二烷基磷酸胆碱胶束以及1,2-二棕榈酰-sn-甘油-3-磷酸胆碱（DPPC）/磷脂酰甘油（PG）7:3（w/w）双层膜中均表现出约80%的α-螺旋含量。带正电荷的赖氨酸残基均匀分布在整个螺旋的圆周上，而螺旋的其他部分为非极性。这与两亲性螺旋中极性和非极性残基的不均匀分布形成鲜明对比。插入DPPC/PG双层膜中的该肽的傅里叶变换红外光谱表明，螺旋轴与脂质酰基链平行排列。这些数据不支持先前的一个假设，即KL4肽与磷脂单层的外围部分相互作用并模拟肺表面活性物质蛋白SP-B，后者由几个两亲性α-螺旋组成。KL4能加速磷脂混合物在气/水界面的铺展，但比所研究的其他跨膜螺旋多肽的效率要低。
