Identification of the DotL coupling protein subcomplex of the Legionella Dot/Icm type IV secretion system.
Legionella pneumophila, the causative agent of Legionnaires' disease, survives in macrophages by altering the endocytic pathway of its host cell. To accomplish this, the bacterium utilizes a type IVB secretion system to deliver effector molecules into the host cell cytoplasm. In a previous report, we performed an extensive characterization of the L. pneumophila type IVB secretion system that resulted in the identification of a critical five-protein subcomplex that forms the core of the secretion apparatus. Here we describe a second Dot/Icm protein subassembly composed of the type IV coupling protein DotL, the apparatus proteins DotM and DotN, and the secretion adaptor proteins IcmS and IcmW. In the absence of IcmS or IcmW, DotL becomes destabilized at the transition from the exponential to stationary phases of growth, concurrent with the expression of many secreted substrates. Loss of DotL is dependent on ClpA, a regulator of the cytoplasmic protease ClpP. The resulting decreased levels of DotL in the icmS and icmW mutants exacerbates the intracellular defects of these strains and can be partially suppressed by overproduction of DotL. Thus, in addition to their role as chaperones for Legionella type IV secretion system substrates, IcmS and IcmW perform a second function as part of the Dot/Icm type IV coupling protein subcomplex.
Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany.
Carr D
CD
Vincent
Jonathan R
JR
Friedman
Kwang Cheol
KC
Jeong
Molly C
MC
Sutherland
Joseph P
JP
Vogel
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems; D016952:Legionella pneumophila / Q000201:enzymology* / Q000235:genetics; D046911:Macromolecular Substances / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization
D001426:Bacterial Proteins; D058947:Bacterial Secretion Systems; C501057:DotL protein, Legionella pneumophila; C503175:IcmS protein, Legionella pneumophila; D046911:Macromolecular Substances; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones