Lipp J, Flint N, Haeuptle M T, Dobberstein B
European Molecular Biology Laboratory, Heidelberg, Federal Republic of Germany.
J Cell Biol. 1989 Nov;109(5):2013-22. doi: 10.1083/jcb.109.5.2013.
We have investigated the structural requirements for the biogenesis of proteins spanning the membrane several times. Proteins containing various combinations of topological signals (signal anchor and stop transfer sequences) were synthesized in a cell-free translation system and their membrane topology was determined. Proteins spanning the membrane twice were obtained when a signal anchor sequence was followed by either a stop transfer sequence or a second signal anchor sequence. Thus, a signal anchor sequence in the second position can function as a stop transfer sequence, spanning the membrane in the opposite orientation to that of the first signal anchor sequence. A signal anchor sequence in the third position was able to insert amino acid sequences located COOH terminal to it. We conclude that proteins spanning the membrane several times can be generated by stringing together signal anchor and stop transfer sequences. However, not all proteins with three topological signals were found to span the membrane three times. A certain segment located between the first and second topological signal could prevent stable membrane integration of a third signal anchor segment.
我们已经多次研究了跨膜蛋白生物合成的结构要求。在无细胞翻译系统中合成了含有各种拓扑信号组合(信号锚定序列和终止转移序列)的蛋白质,并确定了它们的膜拓扑结构。当信号锚定序列后接终止转移序列或第二个信号锚定序列时,可获得跨膜两次的蛋白质。因此,位于第二位的信号锚定序列可作为终止转移序列,以与第一个信号锚定序列相反的方向跨膜。位于第三位的信号锚定序列能够插入其羧基末端的氨基酸序列。我们得出结论,通过将信号锚定序列和终止转移序列串联在一起,可以生成多次跨膜的蛋白质。然而,并非所有具有三个拓扑信号的蛋白质都能跨膜三次。位于第一个和第二个拓扑信号之间的某一段可能会阻止第三个信号锚定片段稳定整合到膜中。