中文摘要：

细菌Ⅳ型分泌系统（type Ⅳ secretion system,T4SS）不仅是农杆菌转运T-DNA的通道,也是多种质粒接合的通道,还能转运多种底物分子到不同的靶细胞（包括细菌和真核细胞）,因此,T4SS的结构及其底物转运机理的研究受到了人们的极大关注,近几年来,这方面的研究进展迅速。农杆菌转运T-DNA的T4SS又叫Vir B/Vir D4系统,是革兰氏阴性菌中最典型的T4SS之一,有关细菌Ⅳ型分泌系统的研究均以农杆菌的Vir B/Vir D4系统为参考模型。现将综述这几年来在农杆菌T4SS结构研究方面取得的最新进展,并介绍目前对T4SS底物转运机理的一些最新认识。

英文摘要：

Type Ⅳ secretion system（T4SS） is not only used for T-DNA transfer by Agrobacterium tumefaciens, but also used for plasmid conjugation by many bacteria. Moreover, many bacteria use T4 SS to translocate various substrates into a wide variety of organisms including bacterial and eukaryotic cells. Therefore, the studies on the structure and substrate-translocating mechanism of T4 SS continue to attract the concentration of researchers and many important progresses in this research field have been made recently. Agrobacterial T4 SS that is used for T-DNA transfer is called Vir B/Vir D4 system, which is one of the best-characterized T4 SSs in Gram-negative bacteria, and thus becomes a typical model of T4 SS. This review highlights the recent breakthroughs in the structural biology of Agrobacterial Vir B/Vir D4 system and summarizes current understanding of the molecular mechanism of T4 SS substrate translocation.