Section of Plant Biology, School of Integrative Plant Sciences (SIPS), Cornell University, Ithaca, NY 14850, USA.
Section of Plant Biology, School of Integrative Plant Sciences (SIPS), Cornell University, Ithaca, NY 14850, USA.
Trends Plant Sci. 2019 Oct;24(10):917-926. doi: 10.1016/j.tplants.2019.06.013. Epub 2019 Jul 9.
Protein amino (N) termini are major determinants of protein stability in the cytosol of eukaryotes and prokaryotes, conceptualized in the N-end rule pathway, lately referred to as N-degron pathways. Here we argue for the existence of N-degron pathways in plastids of apicomplexa, algae, and plants. The prokaryotic N-degron pathway depends on a caseinolytic protease (CLP) S recognin (adaptor) for the recognition and delivery of N-degron-bearing substrates to CLP chaperone-protease systems. Diversified CLP systems are found in chloroplasts and nonphotosynthetic plastids, including CLPS homologs that specifically interact with a subset of N-terminal residues and stromal proteins. Chloroplast N-terminome data show enrichment of classic stabilizing residues [Ala (A), Ser (S), Val (V), Thr (T)] and avoidance of charged and large hydrophobic residues. We outline experimental test strategies for plastid N-degron pathways.
蛋白质氨基（N）末端是真核生物和原核生物细胞质中蛋白质稳定性的主要决定因素，这一概念在 N 末端规则途径中得到了体现，后来又被称为 N 降解途径。在这里，我们提出质体 N 降解途径在顶复门生物、藻类和植物中存在。原核 N 降解途径依赖于一种乳蛋白酶（CLP）S 识别蛋白（接头），用于识别和将带有 N 降解基序的底物递送至 CLP 伴侣蛋白酶系统。多样化的 CLP 系统存在于叶绿体和非光合质体中，包括与一组特定的 N 末端残基和基质蛋白特异性相互作用的 CLPS 同源物。叶绿体 N 末端组学数据显示经典稳定残基[丙氨酸（A）、丝氨酸（S）、缬氨酸（V）、苏氨酸（T）]的富集和避免带电荷和大疏水性残基。我们概述了用于质体 N 降解途径的实验测试策略。
