Li Jianxiong, Wolf Sharon G, Elbaum Michael, Tzfira Tzvi
Department of Biochemistry and Cell Biology, State University of New York, Stony Brook, NY 11794-5215, USA.
Trends Microbiol. 2005 Jul;13(7):295-8. doi: 10.1016/j.tim.2005.05.002.
Type IV secretion systems (T4SSs) are used by various bacteria to deliver protein and DNA molecules to a wide range of target cells. These include systems that are directly involved in pathogenesis, such as the secretion of pertussis toxin by Bordetella pertussis into human cells and the delivery of single-stranded DNA (ssDNA) into plants by Agrobacterium. These complex systems are composed of proteins that span the bacterial cytoplasm. The Agrobacterium T4SS is composed of 12 virulence proteins and delivers its transferred ssDNA and several virulence protein substrates to a variety of eukaryotic cells. Recent studies on the Agrobacterium T4SS have revealed new information on the localization and structure of its proteins in the bacteria, the biochemical properties of its transport signal, the route of a DNA substrate through the secretion system, and the initial point of contact of the system with its host. These findings have expanded our knowledge and understanding of the still mostly obscure structure and function of the T4SSs.
IV型分泌系统（T4SSs）被多种细菌用于将蛋白质和DNA分子传递到广泛的靶细胞。这些系统包括直接参与致病过程的系统，例如百日咳博德特氏菌将百日咳毒素分泌到人体细胞中，以及根癌土壤杆菌将单链DNA（ssDNA）传递到植物中。这些复杂的系统由跨越细菌细胞质的蛋白质组成。根癌土壤杆菌T4SS由12种毒力蛋白组成，并将其转移的ssDNA和几种毒力蛋白底物传递到多种真核细胞中。最近对根癌土壤杆菌T4SS的研究揭示了关于其蛋白质在细菌中的定位和结构、其运输信号的生化特性、DNA底物通过分泌系统的途径以及该系统与其宿主的初始接触点的新信息。这些发现扩展了我们对仍然大多模糊不清的T4SSs结构和功能的认识和理解。
