Decoding the molecular mechanisms of membrane protein targeting and insertion

解读膜蛋白靶向和插入的分子机制

• 批准号: 263098192
• 负责人: Professor Dr. Hans-Georg Koch
• 金额: --
• 依托单位: Institut für Biochemie und Molekularbiologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/263098192?language=en
• 关键词: Decoding; molecular; mechanisms; membrane; protein

The spatial and temporal coordination of protein trafficking is essential in all cells and in particular important for aggregation-prone membrane proteins. The enormous functional heterogeneity of membrane proteins is reflected by their structural diversity, which directly impacts on their insertion mechanism into the membrane. In bacteria, the majority of membrane proteins are co-translationally recognized by the signal recognition particle (SRP), which delivers ribosome-associated nascent proteins (RNCs) to either the SecYEG translocon or the YidC insertase for insertion. How SRP discriminates between both insertion sites is unknown. The SRP receptor FtsY coordinates the transfer of RNCs from SRP to SecYEG, but recent data indicate that FtsY is not required for YidC targeting. This would reflect an unprecedented non-canonical targeting reaction by SRP. Such a role of SRP is also expected during targeting of special membrane proteins, like tail-anchored proteins. Exploring these atypical reactions of SRP further and revealing the interplay of SRP with general chaperone systems will further expand our perception of the immense plasticity of protein targeting systems. The SecYEG translocon forms a highly dynamic protein complex, but the exact function of many of the already known partner proteins and those that we have newly identified is unknown. Our recent data show that some of the accessory proteins reach deeply into the periplasmic vestibule of SecY, which could indicate that they can execute a pulling force on substrates. Different to the dynamic SecYEG translocon, YidC is considered to function as solitary unit during membrane protein insertion. However, a detailed exploration of potential YidC partner proteins in vivo and in vitro is missing. Identifying partner proteins and investigating their function will be in particular revealing in light of recent reports that identified YidC homologues in the archaeal membrane and the ER membrane. This should allow to define similarities and differences of the YidC network in different cellular membranes. Translation-independent targeting of membrane proteins adds yet another variation to bacterial protein insertion mechanisms that needs to be addressed. By combining single molecule in vivo approaches for monitoring mRNA localization in living cells with biochemical tools for determining interaction partners of mRNAs, we will provide insight into this ill-defined process. In summary, this proposal aims to explore the diversity of membrane protein targeting systems, reveal their interaction with general chaperone systems and explore the dynamic assemblies of the SecYEG and YidC insertion sites. This will provide the conceptual framework for understanding the plasticity of protein transport systems that sustain cell viability in pro- and eukaryotes.

蛋白质运输的空间和时间协调对于所有细胞都至关重要，对于易于聚集的膜蛋白尤其重要。膜蛋白巨大的功能异质性反映在其结构多样性上，这直接影响其插入膜的机制。在细菌中，大多数膜蛋白被信号识别颗粒 (SRP) 共翻译识别，信号识别颗粒 (SRP) 将核糖体相关新生蛋白 (RNC) 递送至 SecYEG 易位子或 YidC 插入酶进行插入。 SRP 如何区分两个插入位点尚不清楚。 SRP 受体 FtsY 协调 RNC 从 SRP 到 SecYEG 的转移，但最近的数据表明 YidC 靶向不需要 FtsY。 这将反映出 SRP 前所未有的非规范目标反应。 SRP 的这种作用也在靶向特殊膜蛋白（如尾锚定蛋白）过程中发挥着预期作用。进一步探索 SRP 的这些非典型反应并揭示 SRP 与一般伴侣系统的相互作用将进一步扩大我们对蛋白质靶向系统巨大可塑性的认识。 SecYEG 易位子形成高度动态的蛋白质复合物，但许多已知的伙伴蛋白质和我们新鉴定的蛋白质的确切功能尚不清楚。我们最近的数据表明，一些辅助蛋白深入到 SecY 的周质前庭，这可能表明它们可以对底物产生拉力。与动态 SecYEG 易位子不同，YidC 被认为在膜蛋白插入过程中充当独立单元。然而，缺乏对体内和体外潜在 YidC 伴侣蛋白的详细探索。鉴于最近在古细菌膜和 ER 膜中鉴定出 YidC 同源物的报告，鉴定伴侣蛋白并研究其功能将特别具有启发性。这应该允许定义不同细胞膜中 YidC 网络的相似性和差异。膜蛋白的翻译独立靶向为细菌蛋白插入机制增加了另一种需要解决的变化。通过将监测活细胞中 mRNA 定位的单分子体内方法与确定 mRNA 相互作用伙伴的生化工具相结合，我们将深入了解这一不明确的过程。 总之，本提案旨在探索膜蛋白靶向系统的多样性，揭示其与一般伴侣系统的相互作用，并探索 SecYEG 和 YidC 插入位点的动态组装。这将为理解维持原核生物和真核生物细胞活力的蛋白质运输系统的可塑性提供概念框架。