title: Structure and conservation of the periplasmic targeting factor Tic22 protein from plants and cyanobacteria.
abstract: Mitochondria and chloroplasts are of endosymbiotic origin. Their integration into cells entailed the development of protein translocons, partially by recycling bacterial proteins. We demonstrate the evolutionary conservation of the translocon component Tic22 between cyanobacteria and chloroplasts. Tic22 in Anabaena sp. PCC 7120 is essential. The protein is localized in the thylakoids and in the periplasm and can be functionally replaced by a plant orthologue. Tic22 physically interacts with the outer envelope biogenesis factor Omp85 in vitro and in vivo, the latter exemplified by immunoprecipitation after chemical cross-linking. The physical interaction together with the phenotype of a tic22 mutant comparable with the one of the omp85 mutant indicates a concerted function of both proteins. The three-dimensional structure allows the definition of conserved hydrophobic pockets comparable with those of ClpS or BamB. The results presented suggest a function of Tic22 in outer membrane biogenesis.
authors.affiliation: Department of Biosciences, Goethe University, 60438 Frankfurt, Germany.
authors.forename: Joanna
authors.initials: J
authors.lastname: Tripp
authors.forename: Alexander
authors.initials: A
authors.lastname: Hahn
authors.forename: Patrick
authors.initials: P
authors.lastname: Koenig
authors.forename: Nadine
authors.initials: N
authors.lastname: Flinner
authors.forename: Daniela
authors.initials: D
authors.lastname: Bublak
authors.forename: Eva M
authors.initials: EM
authors.lastname: Brouwer
authors.forename: Franziska
authors.initials: F
authors.lastname: Ertel
authors.forename: Oliver
authors.initials: O
authors.lastname: Mirus
authors.forename: Irmgard
authors.initials: I
authors.lastname: Sinning
authors.forename: Ivo
authors.initials: I
authors.lastname: Tews
authors.forename: Enrico
authors.initials: E
authors.lastname: Schleiff
mesh_terms: D017033:Anabaena / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D000458:Cyanobacteria / Q000378:metabolism* / Q000648:ultrastructure; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008854:Microscopy, Electron; D018832:Molecular Chaperones / Q000378:metabolism; D019897:Periplasm / Q000378:metabolism; D010944:Plants / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D020524:Thylakoids / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D018832:Molecular Chaperones