期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 112, 期 13, 页码 E1678-E1687出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1424655112
关键词
ribosome profiling; protein targeting; plastid; chloroplast; SecA
资金
- German Research Foundation [Zo 302/1-1, Zo 302/2-1]
- National Science Foundation [IOS-1339130]
- Direct For Biological Sciences
- Division Of Integrative Organismal Systems [1339130] Funding Source: National Science Foundation
Chloroplast genomes encode similar to 37 proteins that integrate into the thylakoid membrane. The mechanisms that target these proteins to the membrane are largely unexplored. We used ribosome profiling to provide a comprehensive, high-resolution map of ribosome positions on chloroplast mRNAs in separated membrane and soluble fractions in maize seedlings. The results show that translation invariably initiates off the thylakoid membrane and that ribosomes synthesizing a subset of membrane proteins subsequently become attached to the membrane in a nuclease-resistant fashion. The transition from soluble to membrane-attached ribosomes occurs shortly after the first transmembrane segment in the nascent peptide has emerged from the ribosome. Membrane proteins whose translation terminates before emergence of a transmembrane segment are translated in the stroma and targeted to the membrane posttranslationally. These results indicate that the first transmembrane segment generally comprises the signal that links ribosomes to thylakoid membranes for cotranslational integration. The sole exception is cytochrome f, whose cleavable N-terminal cpSecA-dependent signal sequence engages the thylakoid membrane cotranslationally. The distinct behavior of ribosomes synthesizing the inner envelope protein CemA indicates that sorting signals for the thylakoid and envelope membranes are distinguished cotranslationally. In addition, the fractionation behavior of ribosomes in polycistronic transcription units encoding both membrane and soluble proteins adds to the evidence that the removal of upstream ORFs by RNA processing is not typically required for the translation of internal genes in polycistronic chloroplast mRNAs.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据