Translation into ER Flashcards
Smooth ER produces __ in hepatocytes. In muscle cells it ___.
Smooth ER produces lipid and in muscles cells stores and releases calcium for contraction.
Rough ER has ribosomes on ___. Ribosomes translocate _____ into ____. ER is where ____, ___, and ___ occurs.
Rough ER has ribosomes on its cytoplasmic face. Ribosomes translocate proteins into the RER. The ER is where protein modification, proper protein folding, and assembly of protein subunits occurs.
Free pool of ribosomes go where?
Either translation in cytosol or membrane bound translation.
Ribosomes directed to RER membrane by ___.
Sequence on polypeptide they are translating.
Membrane bound translation steps.
(1) Signal on peptide bound by SRP (signal recognition protein)
(2) GTP binds to complex halting translation
(3) Complex goes and binds to SRP receptor on ER membrane
(4) Protein continues to be translated and is translocated into ER lumen
(5) GTP hydrolyzed and SRP released and recycled
(6) Protein continues to be translated and signal sequence cleaved off by ER signal peptidase.
(7) Ribosome disassociates
Sec61
RER translocator in yeast
Single-pass transmembrane proteins has N-terminus where?
Inside ER lumen
What dictates orientation of protein on ER membrane?
Location of start-stop signal sequence that directs protein to ER and halts insertion into ER – in particular the location of Lys in relation to sequence.
If start-stop sequence preceded by Lys…
If start-stop sequence is followed by Lys
N-terminus will be in cytosol
N -terminus will be in ER lumen
Post-translation translocation: 3 strategies
(1) Direct SRP binding to peptide
(2) Hsp40/Hsc-70-mediated translocation
(3) Get pathway
Get3
An ATPase that transfer tail-anchored protein to the Get1-Get2 complex which inserts protein into membrane
N-linked glycolysation occurs in? On? Uses ___ as a holder of the oligosaccharide.
N-linked glycolysation occurs in RER. On all transmembrane proteins. On first Asn to enter ER lumen. Uses dolichol as holder of oligosaccharide.
GPI anchors
- Added where?
- Attached to what part of protein?
- Proteins that are GPI anchored connect where?
- Proteins in lumen of ER become what?
- Added in RER
- Attached to C-terminus of protein
- Proteins that are GPI anchored connected to outer leaflet
- Proteins in lumen of ER become outside of cell