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Post-Translational Events I

Post-Translational Events I. Translocation of Newly Synthesized Proteins into Membranous Organelles. Locations of Protein Synthesis. ER Associated Ribosomes proteins translocate co-translationally into ER lumen

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Post-Translational Events I

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  1. Post-Translational Events I Translocation of Newly Synthesized Proteins into Membranous Organelles

  2. Locations of Protein Synthesis • ER Associated Ribosomes • proteins translocate co-translationally into ER lumen • subsequent processing & transport through Golgi for secretory vesicles and lysosomes • Cytoplasmic Ribosomes • proteins translocated post-translationally into membranous organelles (except Golgi, ER and lysosome)

  3. Transport of Cytoplasmically Synthesized Proteins • Import into organelles (transmembrane and lumenal) • Mitochondrial import • Chloroplast import • Peroxisome import • Translocation across plasma membrane • Insertion in cytoplasmic face of plasma membrane

  4. Signal Sequences • Portions of protein sequence • Frequently N-terminal, C-terminal • Occasionally located within • Often cleaved following transport event • Signal Recognition Particles/Complexes • protein-translocation channels • escort (chaperone) proteins

  5. Mitochondrial Protein Import • Four Destinations • Outer membrane • Innermembranous space • Inner membrane • Matrix • TOMs • Translocase of the outer mitochondrial membrane • TIMs • Translocase of the inner mitochondrial membrane • Tiny TIMs • escorts of the innermembranous space

  6. TOM & TIM Function

  7. Tiny TIMs and TIM22

  8. TOC & TIC

  9. Peroxisome Import Signal sequence for recognition by PEX5 -SKL-COOH

  10. Peroxisome Formation

  11. Translocation of ER-Associated Ribosome Synthesized Proteins

  12. Docking of Ribosomes to ER Signal peptides typically 10-20 residues – shorter than those on cytostolically synthesized proteins

  13. translocation Ribosome binding Signal peptide binding Signal Recognition Particle • Ribonucleoprotein complex • Similar to bacterial SRP

  14. Translocation of Various Classes of ER Proteins lumenal proteins Type 1 transmembrane proteins Type 2 transmembrane proteins multipass transmembrane proteins

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