Abstract Cyanobacteria are ubiquitous oxygenic photosynthetic bacteria with a versatile metabolism that is highly dependent on effective protein targeting. Protein sorting in diderm bacteria is not trivial and, in cyanobacteria, even less so due to the presence of a complex membrane system: the outer membrane, the plasma membrane and the thylakoid membrane. In cyanobacteria, protein import into the thylakoids is essential for photosynthesis, export to the periplasm fulfills a multifunctional role in maintaining cell homeostasis, and secretion mediates motility, DNA uptake and environmental interactions. Intriguingly, only one set of genes for the general secretory and the twin-arginine translocation pathways seem to be present. However, these systems have to operate in both plasma and thylakoid membranes. This raises the question of how substrates are recognized and targeted to their correct, final destination. Additional complexities arise when a protein has to be secreted across the outer membrane, where very little is known regarding the mechanisms involved. Given their ecological importance and biotechnological interest, a better understanding of protein targeting in cyanobacteria is of great value. This review will provide insights into the known knowns of protein targeting, propose hypotheses based on available genomic sequences and discuss future directions.

中文翻译：

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蓝藻蛋白质易位系统的基因组学见解

摘要 蓝藻是普遍存在的含氧光合细菌，具有高度依赖有效蛋白质靶向的多功能代谢。在双胚层细菌中进行蛋白质分选并非微不足道，在蓝藻中，由于存在复杂的膜系统：外膜、质膜和类囊体膜，蛋白质分选更是如此。在蓝藻中，蛋白质输入类囊体对于光合作用至关重要，输出到周质在维持细胞稳态方面发挥着多功能作用，分泌物介导运动、DNA 吸收和环境相互作用。有趣的是，似乎只存在一组用于一般分泌和双精氨酸易位途径的基因。然而，这些系统必须在质膜和类囊体膜中运行。这就提出了如何识别基材并将其定位到正确的最终目的地的问题。当蛋白质必须跨过外膜分泌时，就会出现额外的复杂性，而关于所涉及的机制知之甚少。鉴于它们的生态重要性和生物技术兴趣，更好地了解蓝藻中的蛋白质靶向具有重要价值。这篇综述将提供对已知蛋白质靶向的见解，根据可用的基因组序列提出假设并讨论未来的方向。更好地了解蓝藻中的蛋白质靶向具有重要价值。这篇综述将提供对已知蛋白质靶向的见解，根据可用的基因组序列提出假设并讨论未来的方向。更好地了解蓝藻中的蛋白质靶向具有重要价值。这篇综述将提供对已知蛋白质靶向的见解，根据可用的基因组序列提出假设并讨论未来的方向。