title: Molecular and structural analysis of Legionella DotI gives insights into an inner membrane complex essential for type IV secretion.
abstract: The human pathogen Legionella pneumophila delivers a large array of the effector proteins into host cells using the Dot/Icm type IVB secretion system. Among the proteins composing the Dot/Icm system, an inner membrane protein DotI is known to be crucial for the secretion function but its structure and role in type IV secretion had not been elucidated. We report here the crystal structures of the periplasmic domains of DotI and its ortholog in the conjugation system of plasmid R64, TraM. These structures reveal a striking similarity to VirB8, a component of type IVA secretion systems, suggesting that DotI/TraM is the type IVB counterpart of VirB8. We further show that DotI and its partial paralog DotJ form a stable heterocomplex. R64 TraM, encoded by the conjugative plasmid lacking DotJ ortholog, forms a homo-hexamer. The DotI-DotJ complex is distinct from the core complex, which spans both inner and outer membranes to form a substrate conduit, and seems not to stably associate with the core complex. These results give insight into VirB8-family inner membrane proteins essential for type IV secretion and aid towards understanding the molecular basis of secretion systems essential for bacterial pathogenesis.
authors.affiliation: Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Kuroda
authors.affiliation: Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Kubori
authors.affiliation: Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Xuan
authors.initials: X
authors.lastname: Thanh Bui
authors.affiliation: Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Hyakutake
authors.affiliation: Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Uchida
authors.affiliation: Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
authors.forename: Katsumi
authors.initials: K
authors.lastname: Imada
authors.affiliation: Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nagai
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D007875:Legionella / Q000502:physiology*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D021381:Protein Transport; D013329:Structure-Activity Relationship; D000069319:Type IV Secretion Systems
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D000069319:Type IV Secretion Systems