Laidler V, Chaddock A M, Knott T G, Walker D, Robinson C
Department of Biological Sciences, University of Warwick, Coventry, United Kingdom.
J Biol Chem. 1995 Jul 28;270(30):17664-7. doi: 10.1074/jbc.270.30.17664.
Proteins are translocated across the thylakoid membrane by two distinct pathways in higher plant chloroplasts, one of which is related to prokaryotic Sec-dependent translocation mechanisms. SecY is an essential, hydrophobic component of the membrane-bound translocase complex in bacteria, and we report here the nucleotide sequence of a full-length cDNA encoding a homolog of SecY from Arabidopsis thaliana. The predicted protein of 551 residues includes an amino-terminal extension of approximately 120 residues when compared with other SecY proteins. The deduced sequence of the mature protein, cpSecY, is 41% identical with SecY from Synechococcus and 33% identical with the Escherichia coli protein. The extension serves to target the protein into chloroplasts; transcription-translation of the cDNA yields a 58-kDa precursor protein which is imported into pea chloroplasts, processed to a product of 46 kDa, and targeted into the thylakoid membrane.
在高等植物叶绿体中，蛋白质通过两种不同途径跨类囊体膜转运，其中一种途径与原核生物依赖Sec的转运机制有关。SecY是细菌中膜结合转运酶复合体的一种必需的疏水性成分，我们在此报道了拟南芥中编码SecY同源物的全长cDNA的核苷酸序列。与其他SecY蛋白相比，预测的由551个残基组成的蛋白质包含一个约120个残基的氨基末端延伸。成熟蛋白cpSecY的推导序列与集胞藻的SecY有41%的同一性，与大肠杆菌蛋白有33%的同一性。该延伸用于将蛋白质靶向叶绿体；cDNA的转录-翻译产生一个58 kDa的前体蛋白，该蛋白被导入豌豆叶绿体，加工成46 kDa的产物，并靶向类囊体膜。
