MCB 2050 FINAL EXAM |34 QUESTIONS WITH ANSWERS
what is the first step of trafficking a protein from the cytoplasm into the nucleus? - --
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? - --
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? - -- 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? - --
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? - -- 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? - -- 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? - -- 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? - -- 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? - -- 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)) - --
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)) - -
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)) - -
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)) - -
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)) - --
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? - --
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? - --
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? - -- 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? - --
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? - -- 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? - -- 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? - -- 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? - -- 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? - -- 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)) - --
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)) - -
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)) - -
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)) - -
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)) - --
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)) - --
