Glossary of Cell Physiology: Chapter 15: Intracellular Compartments and Transport
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- Endomembrane Components
- Er, Golgi, Transport Vesicles, Endosomes, Lysosomes, Vacuoles
- Three Possible Mechanisms of Protein Transport in the cell?
- 1. import into nucleus via nuclear pores
2. import into organelle via protein translocator (mitochondria, chloroplasts, peroxisomes)
3. transport through compartments of the endomembrane system in vesicles
- What regulates passage of materials into and out of the nucleus?
- Signal Sequence which directs protens to the correct location and enables a proten to pass through nuclear pores.
- What materials enter the nucleus?
- nuclear proteins from the cytosol
- What materials leave the nucleus?
- mRNAs, tRNAs, and ribosomal subunits are transported from the nucleus to the cytosol
- What materials both enter and leave the nucleus?
- snRNAs move in both directions
- Describe the nuclear pore complex.
- -single hela cell
-imports 560k ribosomal proteins and exports 14k ribosomal subunits per minute
-octagonals symmetry (30-50 proteins)
- What are nucleoporins?
- the 30-50 proteins that make the octagonal symmetry of a nuclear pore complex.
- Where is the nuclear pore complex found?
- penetrates the inner and outer nuclear membranes
- Nuclear Localization Sequence
- -necessary and sufficient for nuclear targetting
-directs proteins to correct locations
-stretch of AA (one or two short stretches of positively charged AA --arginine (R), lysine (K), histidine (H))
-enables proten to pass through nuclear pores
i.e. w/out sequence, protein remains in cytosol
if basic aa is replaced by nonpolar aa, no nuclear localization
- What is the classic NLS from SV40 T antigen?
- Exportins, Importins?
- export and import into nucleus
- family of proteins function as transport receptors
- How do proteins enter the mitochondria and chloroplasts?
- proteins unfold as they enter
- Signal Peptidase
- cleaves signal sequence
- addition of carbohydrate residues
- Molecular Chaperones (Bip)
- assist in folding
- Protein Disulfide Isomerase
- formation of disulfide bonds
- Where does protein glycosylation occur?
- In the ER
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