Targeting determinants and proposed evolutionary basis for the Sec and the Delta pH protein transport systems in chloroplast thylakoid membranes.
Targeting determinants and proposed evolutionary basis for the Sec and the Delta pH protein transport systems in chloroplast thylakoid membranes.
复制标题
针对叶绿体类囊体膜中SEC和Delta pH蛋白传输系统的决定因素和提议的进化基础。
DOI：
10.1083/jcb.136.4.823
复制
发表时间：
1997-02-24
期刊：
影响因子：
--
通讯作者：
Cline K
中科院分区：
文献类型：
--
作者：
Henry R;Carrigan M;McCaffrey M;Ma X;Cline K
蛋白质向类囊体腔的运输是通过两个类囊体特异性途径完成的，Sec和独特的Delta pH运输系统。通路选择由前体蛋白上的瞬时内腔靶向结构域（LTD）指定。在这里，嵌合和突变的LTD用于鉴定负责靶向特异性的元件。结果表明：（a）由带电荷的N、疏水H和裂解C结构域组成的最小信号肽基序对于途径特异性靶向是必需的且足够的;（B）对Δ pH途径的排他性靶向需要N结构域中的双精氨酸和与Sec途径不相容的H结构域;（c）通过缺乏双精氨酸的N结构域实现对Sec途径的排他性靶向，尽管双精氨酸与Sec系统完全相容。通过结合Delta pH和Sec结构域构建的双靶向信号肽用于同时比较两种途径在面对不同乘客蛋白时的转运能力。而SEC乘客有效地运输这两种途径，三角洲pH乘客被逮捕的SEC途径易位。这一发现表明，三角洲pH机制的发展，以适应运输的蛋白质不兼容的类囊体Sec机械。
Transport of proteins to the thylakoid lumen is accomplished by two precursor-specific pathways, the Sec and the unique Delta pH transport systems. Pathway selection is specified by transient lumen-targeting domains (LTDs) on precursor proteins. Here, chimeric and mutant LTDs were used to identify elements responsible for targeting specificity. The results showed that: (a) minimal signal peptide motifs consisting of charged N, hydrophobic H, and cleavage C domains were both necessary and sufficient for pathway-specific targeting; (b) exclusive targeting to the Delta pH pathway requires a twin arginine in the N domain and an H domain that is incompatible with the Sec pathway; (c) exclusive targeting to the Sec pathway is achieved by an N domain that lacks the twin arginine, although the twin arginine was completely compatible with the Sec system. A dual-targeting signal peptide, constructed by combining Delta pH and Sec domains, was used to simultaneously compare the transport capability of both pathways when confronted with different passenger proteins. Whereas Sec passengers were efficiently transported by both pathways, Delta pH passengers were arrested in translocation on the Sec pathway. This finding suggests that the Delta pH mechanism evolved to accommodate transport of proteins incompatible with the thylakoid Sec machinery.