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http://homepage.univie.ac.at/selma.osmanagic-myers/Zellbiol2.pdf
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VO DIEN : 17.5.2011 12:15-13:45
• Intracellular compartments and protein sorting
Mag. Dr. Selma Osmanagic-Myers
All eucaryotic cells have the same basic set of membrane-enclosed organelles
Evolutionary origins explain the topological relationship of organelles
A possible pathway for the evolution of the cell nucleus and the ER
Mitochondria (and plastids) are thought to have originated when a a bacterium was engulfed by a larger pre-eucaryotic cell
Proteins can move between compartments in different ways
A simplified „roadmap“
of protein traffic
Vesicle budding and fusion during vesicular transport
Signal sequences and patches direct proteins to the correct cell address
The transport of molecules between the nucleus and the cytosol
Nuclear pore complexes perforate the nuclear envelope
Arrangement of the nuclear pore complexes in the nuclear envelope
A model for the gated diffusion barrier of the nuclear pore complex
Nuclear localization signals direct nuclear proteins to the nucleus
Nuclear import receptors bind to both nuclear locali-zation signals and nuclear pore complex proteins
Nucleoporins with tentacle-like fibrils are rich in FG-repeatsto which the nuclear import receptors bind.
The regulation of a monomeric GTPase
The Ran GTPase imposes directionality on transport through nuclear pore complexes
GAP = GTPase-activating protein
GEF = guanine exchange factor
A model explaining how GTP hydrolysis by Ran in the cytosol provides directionality to nuclear transport
How the binding of Ran-GTP can cause nuclear import receptors to release their cargo
The control of nuclear import during T-cell activation
Figure 12-20 Molecular Biology of the Cell (© Garland Science 2008)
Phosphorylation of lamins and nuclear envelope disassembly
The transport of proteins into mitochondria and chloroplasts
Figure 14-37 Molecular Biology of the Cell (© Garland Science 2008)
Mitochondrien und Plastiden
•Bakteriellen Ursprunges•Besitzen eigene DNA (zirkulär), vermehren sich selbstständig•Liefern Energie aus Verbrennung von Nahrung (Mitochondrien)•Und Photosynthese (Plastiden)
Zellteilung der Mitochondrien
•Erfolgt wie bei Prokaryoten durch Furchung. Bei der Zellteilung der Eukaryotenzelle werden die Mitochondrien zufällig auf beide Tochterzellen aufgeteilt.
•Jede Zelle kann einige hundert bis hunderttausende Mitochondrien beinhalten.
•Mitochondrien werden in der Regel nur maternal (über die Oocyte) vererbt.
Figure 2-80 Molecular Biology of the Cell (© Garland Science 2008)
Wege für die Bildung von Acetyl-CoA aus Zuckern und Fetten
Figure 14-3 Molecular Biology of the Cell (© Garland Science 2008)
Elektronentransportprozesse
Figure 14-10 Molecular Biology of the Cell (© Garland Science 2008)
Figure 14-51 Molecular Biology of the Cell (© Garland Science 2008)
Die protonenmotorische Kraft ist die gleiche in Mitochondrien und Chloroplasten
Figure 14-53 Molecular Biology of the Cell (© Garland Science 2008)
Die meisten Proteinen in Mitochondrien werdenvom Zellkern codiert
Figure 14-66 Molecular Biology of the Cell (© Garland Science 2008)
Import kernkodierter Proteine in Mitochondrien
Erfolgt durch Signalpeptide
Translocation into mitochondria depends on signal sequences and protein translocators
Mitochondrial precursor proteins are imported as unfolded polypeptide chains
ATP hydrolysis and a membrane potential drive protein import into the matrix space
Transport into the inner mitochondrial membrane and intermembrane space occurs via several routes
The endoplasmatic reticulum
The ER is structurally and functionally diverse
Co-translational and post-translational protein translocation
Free and membrane-bound ribosomes
Signal sequences were first discovered in proteins imported into the rough ER
A signal-recognition particle (SRP) directs ER signal sequences to a specific receptor in the rough ER membrane
Three ways in which protein translocation can be driven through structurally similar translocators
The ER signal sequence is removed from most soluble proteins after translocation
In single-pass transmembrane proteins, a single internal ER signal sequence remains in the lipid bilayer as a membrane-spanning α helix
Integration of a single-pass transmembrane protein with an internal signal sequence into the ER membrance
Combinations of start-transfer and stop-transfer signals determine the topology of multipass transmembrane proteins
The insertion of the multipass membrane protein rhodopsin into the ER membrane
Most proteins synthesized in the rough ER are glycosylated by the addition of a common N-linked oligosaccaride
Oligosaccarides are used as tags to mark the state of protein folding
Improperly folded proteins are exported from the ER and degraded in the cytosol
Some membrane proteins acquire a covalently attached glycosylphosphatidylinositol (GPI) anchor
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