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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