The DotA protein from Legionella pneumophila is secreted by a novel process that requires the Dot/Icm transporter.
Legionella pneumophila requires the dot/icm genes to create an organelle inside eukaryotic host cells that will support bacterial replication. The dot/icm genes are predicted to encode a type IV-related secretion apparatus. However, no proteins have been identified that require the dot/icm genes for secretion. In this study we show that the DotA protein, which was previously found to be a polytopic membrane protein, is secreted by the Dot/Icm transporter into culture supernatants. Secreted DotA protein was purified and N-terminal sequencing of the purified protein revealed that a 19 amino acid leader peptide is removed from DotA prior to secretion. Extracellular DotA protein did not fractionate in membrane vesicles. Structures containing secreted DotA protein were visualized by electron microscopy and were shaped like hollow rings. These data indicate that the large poly topic membrane protein DotA is secreted from L.pneumophila by a unique process. This represents the first target secreted by the dot/icm-encoded apparatus and demonstrates that this transporter is competent for protein secretion.
Nagai
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Section of Microbial Pathogenesis, Yale University School of Medicine, Boyer Center for Molecular Medicine, 295 Congress Avenue, New Haven, CT 06536, USA.
Roy
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D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006790:Host-Parasite Interactions / Q000502:physiology; D015151:Immunoblotting; D016952:Legionella pneumophila / Q000235:genetics / Q000378:metabolism*; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D015388:Organelles / Q000378:metabolism / Q000648:ultrastructure; D020539:Sequence Analysis, Protein
D001426:Bacterial Proteins; D002352:Carrier Proteins; D017077:Culture Media, Conditioned; C440002:DotA protein, Legionella pneumophila; D046911:Macromolecular Substances; D008565:Membrane Proteins