5ubc

The structure of the Arabidopsis thaliana Toc75 POTRA domains

spinqualitylabelsall models 5ubc, resolution 2.86Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 5ubc is a 2 chain structure with sequence from Arath. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. NonStd Res: MSE Gene: TOC75-3, TOC75, At3g46740, T6H20.230 (ARATH) Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [TC753_ARATH] Essential protein. Mediates the insertion of proteins targeted to the outer membrane of chloroplasts (By similarity). Required for the import of protein precursors into chloroplasts. Forms the voltage-dependent preprotein translocation channels (hydrophilic beta barrel) of the TOC complex in the chloroplastic outer membrane. Publication Abstract from PubMed Protein trafficking across membranes is an essential function in cells; however, the exact mechanism for how this occurs is not well understood. In the endosymbionts, mitochondria and chloroplasts, the vast majority of proteins are synthesized in the cytoplasm as preproteins and then imported into the organelles via specialized machineries. In chloroplasts, protein import is accomplished by the TOC (translocon on the outer chloroplast membrane) and TIC (translocon on the inner chloroplast membrane) machineries in the outer and inner envelope membranes, respectively. TOC mediates initial recognition of preproteins at the outer membrane and includes a core membrane channel, Toc75, and two receptor proteins, Toc33/34 and Toc159, each containing GTPase domains that control preprotein binding and translocation. Toc75 is predicted to have a beta-barrel fold consisting of an N-terminal intermembrane space (IMS) domain and a C-terminal 16-stranded beta-barrel domain. Here we report the crystal structure of the N-terminal IMS domain of Toc75 from Arabidopsis thaliana, revealing three tandem polypeptide transport-associated (POTRA) domains, with POTRA2 containing an additional elongated helix not observed previously in other POTRA domains. Functional studies show an interaction with the preprotein, preSSU, which is mediated through POTRA2-3. POTRA2-3 also was found to have chaperone-like activity in an insulin aggregation assay, which we propose facilitates preprotein import. Our data suggest a model in which the POTRA domains serve as a binding site for the preprotein as it emerges from the Toc75 channel and provide a chaperone-like activity to prevent misfolding or aggregation as the preprotein traverses the intermembrane space. The POTRA domains of Toc75 exhibit chaperone-like function to facilitate import into chloroplasts.,O'Neil PK, Richardson LGL, Paila YD, Piszczek G, Chakravarthy S, Noinaj N, Schnell D Proc Natl Acad Sci U S A. 2017 Jun 13;114(24):E4868-E4876. doi:, 10.1073/pnas.1621179114. Epub 2017 May 30. PMID:28559331 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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