Ridder A N, Kuhn A, Killian J A, de Kruijff B
Department of Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
EMBO Rep. 2001 May;2(5):403-8. doi: 10.1093/embo-reports/kve087.
We have investigated the influence of the different lipid classes of Escherichia coli on Sec-independent membrane protein insertion, using an assay in which a mutant of the single-spanning Pf3 coat protein is biosynthetically inserted into liposomes. It was found that phosphatidylethanolamine and other non-bilayer lipids do not have a significant effect on insertion. Surprisingly, the anionic lipids phosphatidylglycerol and cardiolipin stimulate N-terminal translocation of the protein, even though it has no charged amino acid side chains. This novel effect is general for anionic lipids and depends on the amount of charge on the lipid headgroup. Since the N-terminus of the protein is at least partially positively charged due to a helix dipole moment, apparently negatively charged lipids can stimulate translocation of slightly positively charged protein segments in a direction opposite to the positive-inside rule. A mechanism is proposed to explain these results.
我们利用一种实验方法研究了大肠杆菌不同脂质类别对不依赖Sec的膜蛋白插入的影响，该实验方法是将单跨膜Pf3外壳蛋白的突变体通过生物合成方式插入脂质体中。结果发现，磷脂酰乙醇胺和其他非双层脂质对插入没有显著影响。令人惊讶的是，阴离子脂质磷脂酰甘油和心磷脂能刺激该蛋白的N端转运，尽管该蛋白没有带电荷的氨基酸侧链。这种新效应对于阴离子脂质具有普遍性，并且取决于脂质头部基团的电荷量。由于该蛋白的N端由于螺旋偶极矩至少部分带正电荷，显然带负电荷的脂质可以刺激带轻微正电荷的蛋白片段朝着与正内规则相反的方向转运。我们提出了一种机制来解释这些结果。
