* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Transport of Cytoplasmically Synthesized Proteins into Membranous
Survey
Document related concepts
Homology modeling wikipedia , lookup
Circular dichroism wikipedia , lookup
Protein folding wikipedia , lookup
Protein domain wikipedia , lookup
Bimolecular fluorescence complementation wikipedia , lookup
Protein structure prediction wikipedia , lookup
G protein–coupled receptor wikipedia , lookup
Nuclear magnetic resonance spectroscopy of proteins wikipedia , lookup
SNARE (protein) wikipedia , lookup
Protein moonlighting wikipedia , lookup
Protein purification wikipedia , lookup
Trimeric autotransporter adhesin wikipedia , lookup
Protein mass spectrometry wikipedia , lookup
List of types of proteins wikipedia , lookup
Protein–protein interaction wikipedia , lookup
Transcript
Post-Translational Events I Protein Trafficking Translocation of Newly Synthesized Proteins into Membranous Organelles 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) Routes of Protein Trafficking Copyright 2008 by Saunders/Elsevier. All rights reserved. Graduate students Routes of Intracellular Protein Movement • Cytosolic (free) ribosomes – Cytosolic proteins – Imported into organelles • Mitochondria, Chloroplasts, Peroxisomes, Nucleus – Anchored facing cytoplasmic face of membranes • C-tail anchored proteins in mitochondrial outer membrane and ER membrane • Lipid anchored proteins on inner face of plasma membrane (via ER) • ER-associated ribosomes – Endomembrane system proteins • ER, Golgi, lysosome, vesicles, plasma membrane, secreted proteins Targeting signals that direct proteins synthesized in cytoplasm to organelles Fig. 18-1 Copyright 2008 by Saunders/Elsevier. All rights reserved. Translocons used by polypeptides to cross membranes in eukaryotes Fig. 18-2 Copyright 2008 by Saunders/Elsevier. All rights reserved. Directing Traffic • Signal sequences – Mostly N-terminal, C-terminal – Occasionally internal – Often cleaved following transport event • Signal Recognition Particles – Bind signal sequences • Chaperone proteins – Hsp • Translocons – Protein complexes to move proteins through/into membranes Trafficking of Cytosolically 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 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 • Signal – Presequences – 10-70 a.a. Basic, hydroxylate, & hydrophobic TOM & TIM Function Import of proteins into the mitochondrial matrix Fig. 18-4 Copyright 2008 by Saunders/Elsevier. All rights reserved. Tiny TIMs and TIM22 Facilitate Import into the Inner Membrane Fig. 18-5 Copyright 2008 by Saunders/Elsevier. All rights reserved. TOC & TIC Import of proteins into the chloroplast thylakoid Peroxisome Import •Signal sequences • PTS1 • Recognized by PEX5 • -SKL-COOH • PTS2 • - RLxxxxxH/QL--- Peroxisome Formation Translocation of ER-Associated Ribosome Synthesized Proteins Endoplasmic reticulum (ER) Fig. 20-1 Hypothesis for the evolution of the ER Copyright 2008 by Saunders/Elsevier. All rights reserved. Fluorescence micrograph of a cell with ER marked with a GFP fusion protein Domains of the endoplasmic reticulum Copyright 2008 by Saunders/Elsevier. All rights reserved. Fig. 20-2 Docking of Ribosomes to ER Signal Peptide or Signal Sequence • typically 15-35 residues – shorter than those on cytosolically synthesized proteins – Hydrophobic core of ~6 residues • Examples – MKLSLVAAMLLLLSAARA – MHYCVLSAFLILHLVTVAL – MRPSGTAGAALLALLAALCPRA BiP TGF-b2 EGFR Signal Recognition Particle • Ribonucleoprotein complex Ribosome binding translocation Signal peptide binding Sec61 ER translocon Structure of Sec61 translocon Fig. 20-6 Copyright 2008 by Saunders/Elsevier. All rights reserved. Targeting proteins to the ER lumen & membrane Copyright 2008 by Saunders/Elsevier. All rights reserved. Fig. 20-7 Targeting proteins to the ER membrane Fig. 20-7 Copyright 2008 by Saunders/Elsevier. All rights reserved. Translocation of Various Classes of ER Proteins lumenal proteins Type 1 transmembrane proteins Type 2 transmembrane proteins multipass transmembrane proteins Post-Translational Events II ER & Golgi Processes Rough Endoplasmic Reticulum Glycolsylation • O-linked – serine, threonine, hydroxylysine (collagen) • N-linked - asparagine • The sugars – – – – – – – – GalNac – N-acetylgalactosamine GlcNac – N-acetylglucosamine NANA – N-acetylneuraminic acid (sialic acid) Gal – galactose Glc – glucose Man – mannose Fuc – fucose Dolicholpyrophosphoryl oligosaccharide • All sugars are linked to nucleoside mono- or diphosphate – – – – UDP-gal, UDP-GalNac, UDP-GlcNac GDP-man CMP-NANA Dolichol pyrophosphate Hydroxylated amino acids Glyco-nucleoside Phosphates Dolichol phosphate CMP-N-acetylneuraminic acid CMP-sialic acid UDP-galactose UDP-N-acetylglucosamine GDP-mannose O-linked Glycosylation • Small chains of sugars • N-acetylgalactosamine (GalNac) is first sugar on S orT – GalNac transferase in ER and cis-golgi • Additional sugars added in cis, medial & trans-golgi – Gal added by galactosyl transferase – NANA added last • Each sugar addition is catalyzed by specific enzyme N-linked Glycosylation Initial step in ER • • Dolichol pyrophosphoryl oligosaccharide – 14 sugar moiety attached to dolichol pyrophosphate • (GalNac)2Man9Glc3 – Dolichol phosphate in ER membrane – Sugars added by cytostolic glycosyltransferases – Moiety flips in ER membrane to face lumen – Transferred to asparagine by oligosaccharyl transferase (oligosaccharide-protein transferase) – Target sequence N-X-S and N-X-T (X = P) O- & N-linked Oligosacchari de Chains N-linked Glycolsylation GPI – Linkages • GPI – linked proteins are attached to GPI in ER – GPI in ER membrane – C-term of protein attached to sugar residue on phosphatidyl inositol • GPI linked protein will be attached to outer leaflet of plasma membrane Protein Folding Occurs in ER Lumen Misfolded Proteins Reverse Translocate to Proteasome EDEM Unique Signaling from ER to Make More • Pathway activated by stresses thatER result in more unfolded proteins –heat –unfavorable pHs Unfolded protein responses in the ER lumen Activating transcription factor 6 Fig. 20-11 Inositol requiring 1 PKR-like ERkinase/pancreatic eIF2a kinase Copyright 2008 by Saunders/Elsevier. All rights reserved. Sterol & Lipid Biosynthesis • Phospholgycerides in ER • Sphingolipids in Golgi • Lipid profile asymmetry established via phospholipid exchange proteins and selective vesicular transport due to association between carrier proteins and certain lipid types Regulation of HMG-CoA Reductase On to the Golgi http://youtu.be/rvfvRgk0MfA http://youtu.be/rioXHf97cvs http://youtu.be/u2lieHDDYPY