Type II Secretion System in Legionella

To date L. pneumophila is the only intracellular pathogen known to encode a type II secretion system. Type II machineries are usually associated with organisms that colonize surfaces but do not invade cells. In addition to the prepilin peptidase PilD, which processes pseudopilin (LspG, LspH, LspI, LspJ, LspK) assembly into a functional type II secretion apparatus, the outer membrane secretin LspD, the ATPase LspE, and the inner membrane protein LspF are involved in L.pneumo-phila type II protein secretion. The secretion system is highly conserved in the three sequenced genomes (protein identities of 96-100%) and seems also to be conserved throughout the genus Legionella (Rossier and Cianciotto 2001). The lsp secretion system promotes the ability of L. pneumophila to infect both protozoan and macrophage hosts, to grow in the mammalian lung (Rossier and Cianciotto 2001), and to grow at low temperatures (Soderberg et al. 2004). It is involved in secretion of various enzymes, like the phospholipases A and C, zinc metallopro-tease Msp, several lipases, RNase, pNPPC hydrolase, tartrate-resistant and tar-trate-sensitive acid phosphatase, and lysophospholipase A (Aragon et al. 2001; Flieger et al. 2002; Hales and Shuman 1999; Rossier and Cianciotto 2001).

0 0

Post a comment