BIOC 4580 Lecture Notes - Lecture 26: Oligosaccharyltransferase, Disulfide, Dolichol

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cyanskunk870

23 Mar 2017

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Protein glycosylation occurs step-wise in the lumen of the rer & golgi apparatus, with intervening vesicular traffic. Carbohydrate chains can be n-linked to asn or o-linked to ser/thr, and are derived from a common precursor that is pre- formed on a dolichol-phosphate carrier. Protein folding quality control takes places in the rer lumen; further oligosaccharide processing occurs subsequently in the rer, and in the terminal golgi stacks. Mannose-6-phosphate is used to target enzymes to lysosomes, & the receptor is recycled via the endocytic pathway. Snare proteins are used to effect vesicle fusion by causing membrane buckling , i. e. , inducing curvature. Stages of protein processing in rer & golgi. Signal peptide, leader peptide, signal-anchor, start-transfer, membrane-anchor, reverse signal- anchor, stop-anchor, etc. , sequences determine destination & topology. Variations of protease sensitivity assays are used to study signalling. Pulse chase & protease digestion & detergent permeabilization experiments. Proteomics and/or western blotting can be used to identify proteins.

Related Questions

1. The histones that form the core of the nucleosome get into the nucleus by which of the following?

a) Passive diffusion through nuclear pores

b) Selective and facilitated active transport through nuclear pores

c) Ribosomes located in the nucleus synthetize histones in the nucleus

d) Histones are made at the ER membrane and then diffuse to the nucleus

2. Membrane proteins that belong to the golgi, lysosome, or plasma membrane first pass through which organelle before reaching their final subcellular destination?

a) The golgi apparatus

b) The smooth ER

c) The nucleus

d) The ER membrane

e) The ER lumen

3. Where in the cell would a ribosomal protein be located if it has had its nuclear export signal inactivated (non-functional or non-existent).

a) The protein would be found in the ER lumen

b) The protein would remain in the nucleus

c) The protein would be secreted

d) The protein would remain in the cytoplasm

e) The protein would be in the ER membrane

4. Where would be the final destination of a protein if it contained a NLS anywhere in the protein sequence (and which is exposed to the cytoplasm after protein folding) but also contained an ER signal sequence at the carboxy terminus?

a) The ER lumen

b) The nucleus

c) The cytoplasm

d) The inner nuclear membrane

e) The ER membrane

5. The sequence K-D-E-L serves as a retention/retrieval signal for ER proteins.

a) True

b) False

6. The following are true for both cell membrane proteins and secretory proteins EXCEPT?

a) Precursors of the mature proteins contain signal sequence.

b) Both types of proteins contain stop-transfer sequences

c) Both types of proteins enter the ER while being synthetized

d) Both types of proteins pas through the golgi apparatus

e) Both are carried by clatherin-coated vesicles

7. If you isolate a regulated secreted protein from a secretory/storage vesicle and inject it into the cytosol, is will?

a) Be secreted through channels in the plasma membrane

b) Be taken up into secretory vesicle and secreted

c) Remain in the cytosol until it is degraded

d) Be taken up into the rough ER and follow the secretory pathway

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BIOC 4580 Lecture Notes - Lecture 26: Oligosaccharyltransferase, Disulfide, Dolichol

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