Type IV Secretion Systems in Helicobacter pylori
Wolfgang Fischer, Arno Karnholz, Luisa F. Jimenez-Soto and Rainer Haas
from: Helicobacter pylori: Molecular Genetics and Cellular Biology (Edited by: Yoshio Yamaoka). Caister Academic Press, U.K. (2008)
Type IV secretion systems are widely distributed in prokaryotes, where they are used to deliver DNA or protein substrates to bacterial or eukaryotic target cells. They are structurally complex molecular machines, typically composed of a cell envelope-spanning translocation channel, three cytoplasmic ATPases, and potentially an extracellular pilus structure. The Agrobacterium tumefaciens VirB/D4 type IV secretion system serves as a prototype system for which detailed structural and functional data are available. In H. pylori, three type IV secretion systems have been identified, the ComB, Cag and Tfs3 systems. The ComB system is found in all H. pylori strains and is involved in DNA uptake during natural transformation competence. The Cag type IV secretion system is restricted to a subset of more pathogenic H. pylori strains and mediates transfer of the effector protein CagA into different cell types of the host. The distribution and function of the Tfs3 system is unknown. This review summarizes recent progress in our understanding of the structure, function and regulation of the different type IV secretion systems in H. pylori read more ...