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The type III secretion system needle tip complex mediates host cell sensing and translocon insertion
Author(s) -
Veenendaal Andreas K. J.,
Hodgkinson Julie L.,
Schwarzer Lynn,
Stabat David,
Zenk Sebastian F.,
Blocker Ariel J.
Publication year - 2007
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2007.05620.x
Subject(s) - secretion , biology , type three secretion system , microbiology and biotechnology , shigella flexneri , effector , translocon , transmembrane protein , cell , shigella , virulence , host (biology) , membrane protein , bacteria , membrane , biochemistry , receptor , genetics , gene , escherichia coli , salmonella
Summary Type III secretion systems (T3SSs) are essential virulence determinants of many Gram‐negative bacterial pathogens. The Shigella T3SS consists of a cytoplasmic bulb, a transmembrane region and a hollow ‘needle’ protruding from the bacterial surface. Physical contact with host cells initiates secretion and leads to assembly of a pore, formed by IpaB and IpaC, in the host cell membrane, through which proteins that facilitate host cell invasion are translocated. As the needle is implicated in host cell sensing and secretion regulation, its tip should contain components that initiate host cell contact. Through biochemical and immunological studies of wild‐type and mutant Shigella T3SS needles, we reveal tip complexes of differing compositions and functional states, which appear to represent the molecular events surrounding host cell sensing and pore formation. Our studies indicate that the interaction between IpaB and IpaD at needle tips is key to host cell sensing, orchestration of IpaC secretion and its subsequent assembly at needle tips. This allows insertion into the host cell membrane of a translocation pore that is continuous with the needle.