Biogenesis of beta-barrel proteins of the outer membranes of endosymbiotic organelles
Biochemistry
Cell Biology
Final Report Abstract
The outer membranes (OM) of the endosymbiotically derived organelles mitochondria and plastids form the communication platform between these organelles and the other cell compartments. Consequentially, the proteomes of these membranes were adopted during evolution to fulfill the imposed requirements ranging from exchange of solutes and macromolecules to lipid transfer and signaling. The vast majority of organellar proteins are encoded in the nucleus and synthesized on cytosolic ribosomes. A unique group of such proteins contains those that adopt β-barrel architecture within the outer membranes of both organelles. The delivery of such β-barrel proteins from the cytosol to their target membrane has to be tightly regulated especially in plant cells where the two organelles have to be supplied in parallel while keeping targeting specificity. The targeting signals that define this specificity and the cellular factors that decode them are only partially known. In the first funding period we were able to characterize a new plastidic β-barrel protein and to identify chloroplasts factors like Toc75-V/Oep80 that are involved in the biogenesis of plastidic β-barrel proteins. In addition, we identified the targeting signal of mitochondrial β-barrel proteins and cytosolic factors that keep such proteins in an import competent conformation. In the second funding period, we aimed to decipher further the early stages of the biogenesis of β-barrel proteins both in plant and yeast cells. We were able to identify several cytosolic (co)chaperones that are involved in the early stages of the biogenesis of β-barrel proteins destined to either mitochondria or chloroplasts. Furthermore, we could demonstrate that yeast mitochondria can process artificial de novo designed β-barrel proteins. We further noticed that the two investigated artificial β-barrel proteins depend to a variable extent on mitochondrial import components. Furthermore, we were able to identify the signal that discriminates between mitochondrial and plastidic OM targeting of organellar β-barrel proteins in plants. Additionally, we characterized the topogenic signal of the plastidic factor Toc75/Oep80. We found that an N-terminal cleavable signal is similar to that of the other OMP85 protein present in the OM of chloroplasts and represents unique feature of β-barrel proteins. Moreover, we were able to clarify the topological route of plastidic βbarrel proteins during biogenesis. We could show that the N-termini of these proteins conferred the translocation by the TOC complex, whereas the C-termini convened the membrane integration by Toc75/Oep80. Finally, we identified an intermembrane space protein that interacts with Toc75/Oep80 and forms with it a complex. The protein (accession At5g64816) is equipped with a N-terminal TMD and several CxxxC motifs that are very similar to the small Tim proteins of the mitochondrial intermembrane space that are involved in the biogenesis of β-barrel proteins.
Publications
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The Omp85-type outer membrane protein p36 of Arabidopsis thaliana evolved by recent gene duplication. Journal of Plant Research, 128(2), 317-325.
Nicolaisen, Kerstin; Missbach, Sandra; Hsueh, Yi-Ching; Ertel, Franziska; Fulgosi, Hrvoje; Sommer, Maik S. & Schleiff, Enrico
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Characterization of the targeting signal in mitochondrial β-barrel proteins. Nature Communications, 7(1).
Jores, Tobias; Klinger, Anna; Groß, Lucia E.; Kawano, Shin; Flinner, Nadine; Duchardt-Ferner, Elke; Wöhnert, Jens; Kalbacher, Hubert; Endo, Toshiya; Schleiff, Enrico & Rapaport, Doron
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Mitochondrial-bacterial hybrids of BamA/Tob55 suggest variable requirements for the membrane integration of β-barrel proteins. Scientific Reports, 6(1).
Pfitzner, Anna-Katharina; Steblau, Nadja; Ulrich, Thomas; Oberhettinger, Philipp; Autenrieth, Ingo B.; Schütz, Monika & Rapaport, Doron
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Chloroplast outer envelope protein P39 in
A rabidopsis thaliana belongs to the Omp85 protein family. Proteins: Structure, Function, and Bioinformatics, 85(8), 1391-1401.
Hsueh, Yi‐Ching; Flinner, Nadine; Gross, Lucia E.; Haarmann, Raimund; Mirus, Oliver; Sommer, Maik S. & Schleiff, Enrico
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Cytosolic Hsp70 and Hsp40 chaperones enable the biogenesis of mitochondrial β-barrel proteins. Journal of Cell Biology, 217(9), 3091-3108.
Jores, Tobias; Lawatscheck, Jannis; Beke, Viktor; Franz-Wachtel, Mirita; Yunoki, Kaori; Fitzgerald, Julia C.; Macek, Boris; Endo, Toshiya; Kalbacher, Hubert; Buchner, Johannes & Rapaport, Doron
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The outer membrane Omp85‐like protein P39 influences metabolic homeostasis in mature Arabidopsis thaliana. Plant Biology, 20(5), 825-833.
Hsueh, Y.‐C.; Nicolaisen, K.; Gross, L. E.; Nöthen, J.; Schauer, N.; Vojta, L.; Ertel, F.; Koch, I.; Ladig, R.; Fulgosi, H.; Fernie, A. R. & Schleiff, E.
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The signal distinguishing between targeting of outer membrane β-barrel protein to plastids and mitochondria in plants. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, 1866(4), 663-672.
Klinger, Anna; Gosch, Victoria; Bodensohn, Uwe; Ladig, Roman & Schleiff, Enrico
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Toc75‐V/OEP80 is processed during translocation into chloroplasts, and the membrane‐embedded form exposes its POTRA domain to the intermembrane space. FEBS Open Bio, 10(3), 444-454.
Gross, Lucia E.; Spies, Nicole; Simm, Stefan & Schleiff, Enrico
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Insertion of plastidic β-barrel proteins into the outer envelopes of plastids involves an intermembrane space intermediate formed with Toc75-V/OEP80. The Plant Cell (2021, 2, 24).
Gross, Lucia E; Klinger, Anna; Spies, Nicole; Ernst, Theresa; Flinner, Nadine; Simm, Stefan; Ladig, Roman; Bodensohn, Uwe & Schleiff, Enrico
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The Biogenesis Process of VDAC – From Early Cytosolic Events to Its Final Membrane Integration. Frontiers in Physiology, 12(2021, 8, 12).
Moitra, Anasuya & Rapaport, Doron
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Yeast mitochondria can process de novo designed β‐barrel proteins. The FEBS Journal, 291(2), 292-307.
Moitra, Anasuya; Tiku, Vitasta & Rapaport, Doron
