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          Institute: MPI für Biophysik     Collection: Abt. Strukturbiologie     Display Documents

ID: 571441.0, MPI für Biophysik / Abt. Strukturbiologie
Chloroplast Omp85 proteins change orientation during evolution
Authors:Sommer, Maik S.; Daum, Bertram; Gross, Lucia E.; Weis, Benjamin L. M.; Mirus, Oliver; Abram, Lars; Maier, Uwe-G.; Kühlbrandt, Werner; Schleiff, Enrico
Date of Publication (YYYY-MM-DD):2011
Title of Journal:Proceedings of the National Academy of Sciences of the United States of America
Journal Abbrev.:Proc. Natl. Acad. Sci. USA
Issue / Number:33
Start Page:13841
End Page:13846
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:The majority of outer membrane proteins (OMPs) from Gram- negative bacteria and many of mitochondria and chloroplasts are β-barrels. Insertion and assembly of these proteins are catalyzed by the Omp85 protein family in a seemingly conserved process. All members of this family exhibit a characteristic N-terminal polypep- tide-transport–associated (POTRA) and a C-terminal 16-stranded β-barrel domain. In plants, two phylogenetically distinct and essential Omp85’s exist in the chloroplast outer membrane, namely Toc75-III and Toc75-V. Whereas Toc75-V, similar to the mitochondrial Sam50, is thought to possess the original bacterial function, its homolog, Toc75-III, evolved to the pore-forming unit of the TOC translocon for preprotein import. In all current models of OMP biogenesis and preprotein translocation, a topology of Omp85 with the POTRA do- main in the periplasm or intermembrane space is assumed. Using self- assembly GFP-based in vivo experiments and in situ topology studies by electron cryotomography, we show that the POTRA domains of both Toc75-III and Toc75-V are exposed to the cytoplasm. This un- expected finding explains many experimental observations and requires a reevaluation of current models of OMP biogenesis and TOC complex function.
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Biophysik/Abteilung Strukturbiologie
External Affiliations:Cluster of Excellence Frankfurt, Center for Membrane Proteomics, Goethe University, D-60438 Frankfurt, Germany;
Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, D-60438 Frankfurt, Germany;
Department of Cell Biology, Philipps University, D-35032 Marburg, Germany
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