Kim S J, Robinson C, Mant A
Department of Biological Sciences, University of Warwick, Coventry, UK.
FEBS Lett. 1998 Mar 6;424(1-2):105-8. doi: 10.1016/s0014-5793(98)00148-3.
Two imported thylakoid membrane proteins, PSII-X and PSII-W, are synthesised with cleavable N-terminal signal peptides that closely resemble those of Sec-dependent lumenal proteins. In this report we have reconstituted the insertion of pre-PSII-X and pre-PSII-W into isolated thylakoids. We show that insertion does not require either nucleoside triphosphates or stromal extracts, both of which are required for Sec- and signal recognition particle (SRP)-dependent targeting mechanisms. Insertion is furthermore unaffected by protease treatments that destroy the known protein translocation apparatus in the thylakoid membrane. We conclude that these membrane proteins are inserted by an unusual Sec/SRP-independent mechanism that probably resembles that used by CFoII, and we discuss possible parallels with the biogenesis of phage M13 procoat.
两种导入的类囊体膜蛋白PSII-X和PSII-W是由可裂解的N端信号肽合成的，这些信号肽与依赖Sec的类囊体腔蛋白的信号肽非常相似。在本报告中，我们将前体PSII-X和前体PSII-W插入分离的类囊体中进行了重组。我们发现插入过程既不需要三磷酸核苷，也不需要基质提取物，而这两者都是依赖Sec和信号识别颗粒（SRP）的靶向机制所必需的。此外，插入过程不受蛋白酶处理的影响，蛋白酶处理会破坏类囊体膜中已知的蛋白质转运装置。我们得出结论，这些膜蛋白是通过一种不寻常的不依赖Sec/SRP的机制插入的，这种机制可能类似于CFoII所使用的机制，并且我们讨论了与噬菌体M13前衣壳生物发生可能的相似之处。
