Flashcards
Cellbiology - protein targeting and vesicular transport
Flashcards do conjunto (19)
- 1Protein signal sequenceDirect the protein
to a particular destination
Physical properties (hydrophobicity and charge) decide the direction - 2Nuclear poresMeshwork of proteins:
small water-soluble molecules can pass the nuclear pore
Pore complex proteins
Nuclear basket
Cytosolic fibrils - 3Hur transporteras större molekyler genom membran porerna?M.h.a. nuclear
import receptor (återanvänds)
Nuclear localisation signal
recognized by nuclear
import receptor
• Requires energy (GTP)
• Proteinerna är veckade - 4Cargo proteinprotein som ska transporteras
- 5Transport across membranes by protein translocatorstex mitokondrien, kloroplast mm
Proteiner är oveckat förutom till peroxisomen
- signal sekvensen binder till import receptor protein (a transmembrane protein)
- the receptor brings the protein to the protein translocator in the outer membrane and the protein will start go through the outer membrane
- It will then find (by lateral difussion) the translocator protein in inner membrane. When their almost parallell the protein will go through the inner membrane
Once inside the protein will be folded by chaperon - 6Water-soluble protein delivery to ERThe proteins enter the ER while being synthesized
ER signal sequence on protein binds to SRP (signal-recognition particle) in the cytosol. The SRP also binds to the ribosome.
=> Protein synthesis slows down
SRP binds to SRP receptor in the ER membrane and the ribosome is moved to a protein translocator, which causes the release of SRP and the protein synthesis begins again at the same time as the protein goes through the membrane
Signal peptidase then cleaves the signal sequence that will be degraded in the bilayer - 7Transport of transmembrane proteins from cytosol to ERthe protein have a hydrophobic start and stop sequence
- 8Vesicle buddingCargo receptor binds to cargo protein
adaptin binds to the cargo receptor and starts to form a vesicle.
Dynamin cuts of the membrane.
Uncoating of the clathrin coat => naked transport vesicle - 9Vesicle docking to deliver cargoRab proteins on the vesicle recognizes tethering proteins on the membrane
v-SNARE on vesicle binds to t-SNARE on membrane and bring the vesicle closer to the membrane
the cargo protein is delivered and membranes fuse togheter - 10Protein modification in ER• Disulfide bonds → stabilize structure
• Glycosylation → protect to degradation, transport signal, glycocalyx - 11Protein quality control before ER exit• ER retention signal → proteins stays and functions in ER
• Chaperone proteins → prevent exit of misfolded proteins - 12Golgi apparatusCis to trans
- protein modification
- protein sorting - 13Exocytosis= transport from trans-Golgi to plasma membrane
- 14Constitutive (unregulated) exocytosis pathway• supply of new lipids and proteins to plasma membrane: cell expansion, renewing
• secretion: further diffusion to other cells - 15Regulated exocytosis pathwayonly in specific type of cells: secretory cells
• secretory proteins stored in secretory vesicles
• extracellular signal needed - 16Endocytic pathways• the material is enclosed by plasma membrane → intracellular
endocytic vesicle → delivery to endosomes
1. Pinocytosis = cellular drinking, by all cells
2. Phagocytosis = cellular eating, by phagocytic cells like
macrophages, neutrophils
3. Receptor-mediated endocytosis = specific uptake to avoid large
volumes or unnecessary compounds) - 17Tissue= assembly of cells
4 types of tissue: muscular, nervous, connective, epithelial - 18Epithelia= sheet of cells covering an
external face or lining an internal body
cavity
a large variation
The cells are polarized:
APICAL side: at luminal area (= the inner open space or cavity of a tubular organ)
BASAL side: at basal lamina
BASAL LAMINA: sheet of collagen and
laminin – link to other tissue (The basal lamina is a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits.) - 19Types of cell junctionsClassification according to their function:
1. Tight junctions: seal
- Composed of occludins and claudins
2. Adherens junctions: attachments
Linked to cytoskeleton by:
- adherens junctions (between epithelial cells) or
- desmosome (between epithelial cells) or
- hemidesmosome (between epithelial cell and basal lamina)
3. Gap junctions: communications
- passive diffusion of inorganic ions
and water-soluble molecules (1kDa)
- 6 protein subunits called connexon;
2 connexons form a gap junction
- Electrical and metabolic coupling
between cells (cardiac muscle cells)
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- Criado por Tova A · 5 fev 2021
- Copiado por Tova A · 19 fev 2021
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