biostudies-literatureUnknown111(32)Kubori TBacterial type IV secretion systems are evolutionarily related to conjugation systems and play a pivotal role in infection by delivering numerous virulence factors into host cells. Using transmission electron microscopy, we report the native molecular structure of the core complex of the Dot/Icm type IV secretion system encoded by Legionella pneumophila, an intracellular human pathogen. The biochemically isolated core complex, composed of at least five proteins--DotC, DotD, DotF, DotG, and DotH--has a ring-shaped structure. Intriguingly, morphologically distinct premature complexes are formed in the absence of DotG or DotF. Our data suggest that DotG forms a central channel spanning inner and outer membranes. DotF, a component dispensable for type IV secretion, plays a role in efficient embedment of DotG into the functional core complex. These results highlight a common scheme for the biogenesis of transport machinery.Proceedings of the National Academy of Sciences of the United States of America11804-9https://www.ebi.ac.uk/biostudies/studies/S-EPMC4136560biostudies-literatureNative structure of a type IV secretion system core complex essential for Legionella pathogenesis.PMC4136560Nagai HHigaki SAizawa SBui XTKoike MKubori TfalseNative structure of a type IV secretion system core complex essential for Legionella pathogenesis.Bacterial type IV secretion systems are evolutionarily related to conjugation systems and play a pivotal role in infection by delivering numerous virulence factors into host cells. Using transmission electron microscopy, we report the native molecular structure of the core complex of the Dot/Icm type IV secretion system encoded by Legionella pneumophila, an intracellular human pathogen. The biochemically isolated core complex, composed of at least five proteins--DotC, DotD, DotF, DotG, and DotH--has a ring-shaped structure. Intriguingly, morphologically distinct premature complexes are formed in the absence of DotG or DotF. Our data suggest that DotG forms a central channel spanning inner and outer membranes. DotF, a component dispensable for type IV secretion, plays a role in efficient embedment of DotG into the functional core complex. These results highlight a common scheme for the biogenesis of transport machinery.2014-01-01T00:00:00Z2014 Aug2025-04-19T11:18:41.323Z2019-03-27T01:34:16ZS-EPMC41365602506269310.1073/pnas.1404506111