Structural and functional analysis of multiprotein complexes required for colicin translocation

细菌细胞可以从细胞质中输出许多蛋白质到细胞外，包括能够对接触它们的人类造成伤害的毒素。在过去的20年里，蛋白质输出的机制已经得到了很好的描述。相比之下，蛋白质从外部进入细菌细胞是一种罕见的事件，仅限于粘菌；细菌产生的蛋白质抗生素，用来杀死近亲物种以获得选择优势。一个例子是大肠杆菌素E9，它具有具有脱氧核糖核酸酶（DNase）活性的c端细胞毒性结构域。如果进入大肠杆菌细胞，DNA酶会攻击并降解细胞质中的DNA，导致细胞死亡。细胞毒性dna酶结构域从细胞外传递到细胞质的过程称为易位，涉及大肠杆菌蛋白E9的n端易位结构域与许多大肠杆菌蛋白的相互作用。涉及易位结构域的蛋白质-蛋白质相互作用如何导致dna酶结构域进入细胞质的分子细节尚不清楚。该项目旨在生成数据，以便制定更好的迁移过程模型。我们提出的研究对开发新的抗生素和提高我们对蛋白质复合物形成过程的理解具有潜在的意义。

Bacterial cells can export many proteins from the cytoplasm to the outside of the cell, including toxins that are capable of causing damage to humans that come into contact with them. The mechanisms of protein export have been well characterised in the last 20 years. In contrast the import of proteins into bacterial cells from the outside is a rare event that is limited to colicins; protein antibiotics produced by bacteria to kill closely related species in order to gain a selective advantage. An example is colicin E9 which has a C-terminal cytotoxic domain that has deoxyribonuclease (DNase) activity. If delivered into E.coli cells the DNase attacks and degrades their DNA in the cytoplasm and leads to cell death. The process by which the cytotoxic DNase domain is delivered from outside the cell into the cytoplasm is called translocation, and involves the interaction of the N-terminal translocation domain of colicin E9 with a number of E.coli proteins. The molecular details of how the protein-protein interactions involving the translocation domain result in the delivery of the DNase domain into the cytoplasm are poorly understood. This project aims to generate data so that better models of the translocation process can be formulated. Our proposed studies have potential implications in the development of new antibiotics and improving our understanding of the process by which complexes of proteins are formed.