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Identification of the core transmembrane complex of the Legionella Dot/Icm type IV secretion system
Author(s) -
Vincent Carr D.,
Friedman Jonathan R.,
Jeong Kwang Cheol,
Buford Emily C.,
Miller Jennifer L.,
Vogel Joseph P.
Publication year - 2006
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.1365-2958.2006.05446.x
Subject(s) - biology , secretion , transmembrane protein , legionella , plasmid , bacterial outer membrane , membrane protein , type three secretion system , microbiology and biotechnology , bacteria , dna , genetics , gene , escherichia coli , membrane , biochemistry , virulence , receptor
Summary Type IV secretion systems (T4SS) are utilized by a wide range of Gram negative bacteria to deliver protein and DNA substrates to recipient cells. The best characterized T4SS are the type IVA systems, which exhibit extensive similarity to the Agrobacterium VirB T4SS. In contrast, type IVB secretion systems share almost no sequence homology to the type IVA systems, are composed of approximately twice as many proteins, and remain largely uncharacterized. Type IVB systems include the Dot/Icm systems found in the pathogens Legionella and Coxiella and the conjugative apparatus of IncI plasmids. Here we report the first extensive characterization of a type IVB system, the Legionella Dot/Icm secretion apparatus. Based on biochemical and genetic analysis, we discerned the existence of a critical five‐protein subassembly that spans both bacterial membranes and comprises the core of the secretion complex. This transmembrane connection is mediated by protein dimer pairs consisting of two inner membrane proteins, DotF and DotG, which are able to independently associate with DotH/DotC/DotD in the outer membrane. The Legionella core subcomplex appears to be functionally analogous to the Agrobacterium VirB7‐10 subcomplex, suggesting a remarkable conservation of the core subassembly in these evolutionarily distant type IV secretion machines.