MCB 2050 FINAL EXAM QUESTIONS AND ANSWERS
What is the first step of trafficking a protein from the cytoplasm into the nucleus? -
answers - - nascent (newly synthesized cargo protein bound with a nls) is recognized by
another protein called, importin.
- importin a (alpha) binds to basic residues (amino groups) of cargo protein nls.
- importin b (beta) binds to importin a (alpha) creating an importin a/b complex
What is the second step of trafficking a protein from the cytoplasm into the nucleus? -
answers - - importin a/b complex moves through cytoplasm towards the nucleus
- once surface of the nucleus has been reached, importin b binds cytoplasmic filaments
at npc (nuclear pore complex)
What is the third step of trafficking a protein from the cytoplasm into the nucleus? -
answers - - the importin cargo complex which is stuck to the npc cytoplasmic filaments,
moves through the fg domain to the nucleus
What is the fourth step of trafficking a protein from the cytoplasm into the nucleus? -
answers - - once importin cargo complex enters the nucleus, ran-gtp binds to importin b
and causes the dissociation of the importin cargo complex
- disassociated cargo protein is released into the nucelus and the nes (nuclear export
signal) on importin a is exposed
- ran-gtp (still bound to importin b), moves down ran-gtp gradient and back through the
npc into the cytoplasm and taking importin b with it (moving from the nucleus to
cytoplasm) recycling
- once ran-gtp is in the cytoplasm is hydrolyzed (via ran-gap1), forms ran-gdp and
importin b is released
- ran-gdp flows down concentration gradient into nucleus where it is converted back into
ran-gtp (via rcc1) recycling
What is step five of trafficking a protein from the cytoplasm into the nucleus? - answers -
- an exportin (karyopherin) binds to importin a via newly exposed nes; ran-gtp also
binds exportin
- export complex moves down the ran-gtp gradient through the npc into the cytoplasm
- cytoplasmic enzyme ran-gap1 aids in the conversion of ran-gtp to ran-gsp and export
complex disassociates
- ran-gdp moves down the ran-gdp gradient into the nucleus where it is converted back
into ran-gtp by nuclear enzyme rcc1, maintaining a high ran-gtp in the nucleus. Exportin
moves back into the nucleus (via importin) for another round of export
What is the first step involved in cotranslational insertion of a single-spanning,
endoplasmic reticulum (er) integral membrane protein that possesses an n cytoplasm -
c lumen topology? - answers - - n-terminus of the nascent polypeptide enters the sec61
translocon
, - growing protein transmembrane domain (tmd) enters the interior of the translocon
- tmd stops any further translocation of the nascent protein through the translocon
channel
What is the second step involved in cotranslational insertion of a single-spanning,
endoplasmic reticulum (er) integral membrane protein that possesses an n cytoplasm -
c lumen topology? - answers - - translocon's interior interacts with the protein's tmd to
stop translocation, with several positively charged amino acid residues located just
upstream (n terminal) of the tmd (positive - outside rule)
What is the third step involved in cotranslational insertion of a single-spanning,
endoplasmic reticulum (er) integral membrane protein that possesses an n cytoplasm -
c lumen topology? - answers - - synthesis of protein's c terminus resumes through
translocon into lumen
What is the fourth step involved in cotranslational insertion of a single-spanning,
endoplasmic reticulum (er) integral membrane protein that possesses an n cytoplasm -
c lumen topology? - answers - - final membrane orientation is n cytoplasm - c lumen
What is the first step involved in one of the two unfolded protein response pathways
discussed in class? (perk-mediated upr pathway (protein kinase rna-like er kinase)) -
answers - - bip (binding immunoglobulin protein) is released from perk (on
transmembrane) in order to aid in the folding of accumulating misfolded proteins
What is the second step involved in one of the two unfolded protein response pathways
discussed in class? (perk-mediated upr pathway (protein kinase rna-like er kinase)) -
answers - perk dimerizes (attaches to another perk) and becomes active
What is the third step involved in one of the two unfolded protein response pathways
discussed in class? (perk-mediated upr pathway (protein kinase rna-like er kinase)) -
answers - cytoplasmic-facing kinase domains of activated perk phosphorylates to elf2a
(inhibiting it from further translation)
- er stress is alleviated or (if not) cell death (apoptosis) occurs
What is the first step involved in one of the two unfolded protein response pathways
discussed in class? (atf6-mediated upr pathway (activating transcription factor 6)) -
answers - process beings in er lumen ---> travelling through cytosol ---> nucleus
- bip is released from atf6
What is the second step involved in one of the two unfolded protein response pathways
discussed in class? (atf6-mediated upr pathway (activating transcription factor 6)) -
answers - - the release of bip allows atf6 to become active and travel from the er
transmembrane to the golgi
What is the third step involved in one of the two unfolded protein response pathways
discussed in class? (atf6-mediated upr pathway (activating transcription factor 6)) -
What is the first step of trafficking a protein from the cytoplasm into the nucleus? -
answers - - nascent (newly synthesized cargo protein bound with a nls) is recognized by
another protein called, importin.
- importin a (alpha) binds to basic residues (amino groups) of cargo protein nls.
- importin b (beta) binds to importin a (alpha) creating an importin a/b complex
What is the second step of trafficking a protein from the cytoplasm into the nucleus? -
answers - - importin a/b complex moves through cytoplasm towards the nucleus
- once surface of the nucleus has been reached, importin b binds cytoplasmic filaments
at npc (nuclear pore complex)
What is the third step of trafficking a protein from the cytoplasm into the nucleus? -
answers - - the importin cargo complex which is stuck to the npc cytoplasmic filaments,
moves through the fg domain to the nucleus
What is the fourth step of trafficking a protein from the cytoplasm into the nucleus? -
answers - - once importin cargo complex enters the nucleus, ran-gtp binds to importin b
and causes the dissociation of the importin cargo complex
- disassociated cargo protein is released into the nucelus and the nes (nuclear export
signal) on importin a is exposed
- ran-gtp (still bound to importin b), moves down ran-gtp gradient and back through the
npc into the cytoplasm and taking importin b with it (moving from the nucleus to
cytoplasm) recycling
- once ran-gtp is in the cytoplasm is hydrolyzed (via ran-gap1), forms ran-gdp and
importin b is released
- ran-gdp flows down concentration gradient into nucleus where it is converted back into
ran-gtp (via rcc1) recycling
What is step five of trafficking a protein from the cytoplasm into the nucleus? - answers -
- an exportin (karyopherin) binds to importin a via newly exposed nes; ran-gtp also
binds exportin
- export complex moves down the ran-gtp gradient through the npc into the cytoplasm
- cytoplasmic enzyme ran-gap1 aids in the conversion of ran-gtp to ran-gsp and export
complex disassociates
- ran-gdp moves down the ran-gdp gradient into the nucleus where it is converted back
into ran-gtp by nuclear enzyme rcc1, maintaining a high ran-gtp in the nucleus. Exportin
moves back into the nucleus (via importin) for another round of export
What is the first step involved in cotranslational insertion of a single-spanning,
endoplasmic reticulum (er) integral membrane protein that possesses an n cytoplasm -
c lumen topology? - answers - - n-terminus of the nascent polypeptide enters the sec61
translocon
, - growing protein transmembrane domain (tmd) enters the interior of the translocon
- tmd stops any further translocation of the nascent protein through the translocon
channel
What is the second step involved in cotranslational insertion of a single-spanning,
endoplasmic reticulum (er) integral membrane protein that possesses an n cytoplasm -
c lumen topology? - answers - - translocon's interior interacts with the protein's tmd to
stop translocation, with several positively charged amino acid residues located just
upstream (n terminal) of the tmd (positive - outside rule)
What is the third step involved in cotranslational insertion of a single-spanning,
endoplasmic reticulum (er) integral membrane protein that possesses an n cytoplasm -
c lumen topology? - answers - - synthesis of protein's c terminus resumes through
translocon into lumen
What is the fourth step involved in cotranslational insertion of a single-spanning,
endoplasmic reticulum (er) integral membrane protein that possesses an n cytoplasm -
c lumen topology? - answers - - final membrane orientation is n cytoplasm - c lumen
What is the first step involved in one of the two unfolded protein response pathways
discussed in class? (perk-mediated upr pathway (protein kinase rna-like er kinase)) -
answers - - bip (binding immunoglobulin protein) is released from perk (on
transmembrane) in order to aid in the folding of accumulating misfolded proteins
What is the second step involved in one of the two unfolded protein response pathways
discussed in class? (perk-mediated upr pathway (protein kinase rna-like er kinase)) -
answers - perk dimerizes (attaches to another perk) and becomes active
What is the third step involved in one of the two unfolded protein response pathways
discussed in class? (perk-mediated upr pathway (protein kinase rna-like er kinase)) -
answers - cytoplasmic-facing kinase domains of activated perk phosphorylates to elf2a
(inhibiting it from further translation)
- er stress is alleviated or (if not) cell death (apoptosis) occurs
What is the first step involved in one of the two unfolded protein response pathways
discussed in class? (atf6-mediated upr pathway (activating transcription factor 6)) -
answers - process beings in er lumen ---> travelling through cytosol ---> nucleus
- bip is released from atf6
What is the second step involved in one of the two unfolded protein response pathways
discussed in class? (atf6-mediated upr pathway (activating transcription factor 6)) -
answers - - the release of bip allows atf6 to become active and travel from the er
transmembrane to the golgi
What is the third step involved in one of the two unfolded protein response pathways
discussed in class? (atf6-mediated upr pathway (activating transcription factor 6)) -
