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Biology 2382B Lecture Notes - Lecture 4: Secretion, Signal Peptidase, Translocon

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bluerat937
23 Mar 2014
School
Western University
Department
Biology
Course
Biology 2382B
Professor
Robert Cumming

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Document Summary

Translocation and translation occur simultaneously due to signal sequence being at. Delivers ribosome/nascent polypeptide complex to srp receptor in er membrane. Cellular pathway for synthesizing and sorting soluble and membrane proteins localized to the. Secretory proteins only degraded if treated with detergent first to destroy membrane. Indicates that newly made proteins are made/transported to lumen of rough er. Proteins in cytosol kept unfolded by bound chaperones. Protein binds to import receptor in outer membrane (close to inner membrane) Protein moves through channel and adjacent channel in inner membrane. Chaperonin- actively facilitate protein folding in a process that depends on atp. Transfer of ribosome/nascent polypeptide complex leads to opening of translocon. Srp and srp receptor dissociate and gtp is hydrolyzed. Signal sequence cleaved in er lumen by signal peptidase. Translocon closes and protein folds to native conformation. N-linked oligosaccharides; attached to amide nitrogen of asparagine.

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Related Questions

1. Which cytosolic factor is most likely to associate with the signal sequence of a protein that is targeted co-translationally to the ER?

A chaperone of the Hsp70 family

The translocation channel

The ribosome

Signal recognition particle (SRP)

Signal peptidase

2. What is the most likely fate of a protein with an N-terminal hydrophobic sorting signal and an additional internal hydrophobic domain of 22 amino acids?

The protein stays in the cytosol

The protein is transported to mitochondria

Because the protein has an N-terminal sorting signal, the protein is translocated all the way into the ER lumen

The hydrophobic domain is recognized as a transmembrane domain once it is in the translocation channel and released sideways into the membrane

The hydrophobic domain is cleaved off by signal peptidase

3. Which of the following statements best describes N-glycosylation? N-glycosylation refers to........

the addition of a pre-formed sugar tree to a serine or threonine present in the cytosolic domain of a protein

the addition of a pre-formed sugar tree to a phospholipid to make a glycolipid

the addition of individual sugars to selected amino acids on a protein

the addition of a pre-formed sugar tree to an asparagine residue found within the consensus sequence Asn-X-Ser/Thr in an ER lumenal domain of a protein

the addition of a pre-formed sugar tree to an asparagine residue found within the consensus sequence Asn-X-Ser/Thr in a cytosolic domain of a protein

4. What is the most likely fate of a protein in which a mutation has led to misfolding in the ER?

It is sequestered by the proteasome in the cytosol

It is first tagged with ubiquitin in the ER and then degraded by the proteasome in the cytosol

It is first moved out of the ER, tagged with ubiquitin in the cytosol and then degraded by the proteasome in the cytosol

It associates with many chaperones in the ER, which guarantee its correct folding

Its misfolded state is recognized by chaperones in the ER, which will induce the protein's degradation by the proteasome in the ER.

True or False? True False
1. Proteins rapidly pass artificial membrane (liposome).--------------------------------------------------------------------------------------( ) ( )
2. Amphiphatic detergent such as SDS spontaneously forms bilayer inwater. ------------------------------------------------------------( ) ( )
3. Cholesterol does have a hydrophilic head and hydrophobic tail.-------------------------------------------------------------------------( ) ( )
4. Fat molecules are one of the major components of the plasmamembrane.------------------------------------------------------------- ( ) ()
5. Phospholipid molecules such as phosphatidylcholine spontaneouslyform bilayer. ----------------------------------------------------( ) ( )
6. Flippase facilitates lateral movement of phospholipids withinthe plane of the membrane.----------------------------------------- ( ) ( )
7. Glycolipids make bilayer less permeable to small water solublemolecules.----------------------------------------------------------- ( ) ()
8. Membrane inner leaflet is enriched with phosphatidylcholine,Sphingomyelin, and Glycolipid. -----------------------------------( ) ( )
9. Plasma membrane proteins can have an enzyme activity.--------------------------------------------------------------------------------( ) ( )
10. A single pass membrane protein must have an amphiphatic alphahelix.-------------------------------------------------------------- ( )( )
11. Plasma membrane proteins can be linked to a lipid molecule atthe outer leaflet of the plasma membrane. --------------------- ( )( )
12. The lateral motility of membrane proteins can be restricted bytight junctions.------------------------------------------------------ ( ) ()
13. Channel proteins have specific binding sites for ions and thusslower than carrier proteins.--------------------------------------- ( ) ( )
14. An antiport would function as a symport if its orientation inthe membrane were reversed. ---------------------------------------( ) ( )
15. A transmembrane pore can be formed by multiple amphipathicalpha helices. ----------------------------------------- ( ) ()
16. Porin proteins form water-filled channels in the outer membraneof a bacterium and are mostly composed of beta sheets. ---- ( ) ()
17. Glucose uniporters localize at the apical side of theintestinal epithelium.------------------------------------------------------------ ( ) ()
18. GAP junction is a selective pore for anions.-----------------------------------------------------------------------------------------------( ) ( )
19. A voltage-gated Na+ channel adopts only two conformationstates: open and closed.----------------------------------------------- ( ) ( )
20. Voltage gated K+ channel opens faster than the Voltage gatedNa+ channels.-------------------------------------------------------- ( ) ()
21. Opening of chloride channel at the synapse will help to fire anaction potential.------------------------------------------------------ ( ) ()
22. The nuclear pore complex forms a gate through which moleculespass the nucleus uni-directionally. -------------------- ( ) ()
23. A completely folded protein is imported into a mitochondrionthrough a large non-selective pore.--------------------------------- ( ) ( )
24. ER signal sequence contains multiple lysine and arginineresidues.----------------------------------------------------------------------( ) ( )
25. The plasma membrane is a sorting station of inward endocyticpathway.---------------------------------------------------------------- () ( )
26. The trans Golgi functions as a sorting station of outwardsecretory pathway.----------------------------------------------------------- ( ) ()
27. Vesicles budding from ER are coated with Clathrin.----------------------------------------------------------------------------------------( ) ( )
28. RabGTPases and tethering proteins are the major specificitydeterminant of vesicle transport system. --------------------------( ) ( )
29. v-SNARE proteins are one of the tethering proteins.------------------------------------------------------------------------------------( ) ( )
30. In secretory cells, the constitutive and regulatory pathways ofexocytosis diverge at the cis Golgi network. ------------------ ( )( )
31. Many proteins are posttranslationally glycosylated at tyrosineresidues in the ER.------------------------------------------------- ( ) ( )
32. Cells import LDL molecules exclusively through pinocytosis.-------------------------------------------------------------------------( ) ( )
33. Cells recycle LDL receptors from lysosome to the plasmamembrane.----------------------------------------------------------------- () ( )
34. Phagosomes fuse with late endosome.------------------------------------------------------------------------------------------------------( ) ( )
35. Small vesicles from ER near the plasma membrane can fuse withthe plasma membrane upon bypassing Golgi apparatus. -- ( ) ()
36. If a Sec mutant showed an accumulation of newly synthesizedproteins at ER,
then the Sec gene is likely a component of vesicle-buddingmachinery of trans-Golgi network.------------------------------------ ( ) ( )
37. A signal recognition particle is a single pass trans-membraneprotein of the ER membrane.---------------------------------------- ( ) ( )
38. Typical animals cells display higher levels of intracellularsodium than extracellular compartments.------------------------------ ( ) ( )
39. Typical animals cells display higher levels of intracellularchloride than extracellular compartments.----------------------------- ( ) ( )
40. The Na-K Pump is a GTPase that can adopt active and inactiveconformational states.----------------------------------------------- ( ) ( )
1. Phospholipase
C-­-ß
produces
phosphatidylinositol
3,4,5-­-trisphosphate
and
diacylglycerol.
(
)
(
)
2. PDGF
activates
GPCR.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­----­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
3. Rho
is
an
example
of
heterotrimeric
G
proteins.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­----­--­--­--­--­--­-
(
)
(
)
4. All
members
of
the
G
protein
coupled
receptors
interact
with
small
GTPase
Ras.
-­--­--­--­--­--­--­--­--­--­-
(
)
(
)
5. Adrenaline
is
an
example
of
the
ligands
for
the
RPTK
family.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
6. Ras
GEF
activates
RPTK.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­----­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
7. PH
domain
containing
proteins
bind
to
activated
EGFR.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
8. Ligands
for
GPCR
proteins
induce
dimerization
of
the
receptor.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
9. Grb2
is
an
adaptor
protein
that
binds
to
a
phospho-­-tyrosine
residue
of
activated
RPTK
through
a
PH
domain.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­----­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
10. When
a
cell
is
expressing
a
large
number
of
dominant
negative
EGFR
proteins,
an
introduction
of
a
constitutively
active
Ras
mutant
will
allow
EGF
signaling.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
11. PI3K
generates
phosphatidylinositol
3,4,5-­-trisphosphate
from
IP3.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
12. Calcium
inhibits
PKC.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­----­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
13. cAMP
activates
PKA.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­----­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
14. The
MAP
kinase
ERK
inhibits
MAP
kinase
kinases.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­----­--­-
(
)
(
)
15. cAMP
is
an
example
of
a
first
messenger.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­----­--­--­--­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
16. All
7-­-Transmembrane
receptors
are
G
Protein
Coupled
Receptors.
-­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
17. Both
Ga
and
Gß
subunits
of
the
heterotrimeric
G
protein
can
mediate
GPCR
signaling.
-­--­--­-
(
)
(
)
18. Both
Ga
and
Gß
subunits
of
the
heterotrimeric
G
protein
have
GTPase
activity.
-­--­--­--­--­--­--­--­--­--­--­--­-
(
)
(
)
19. The
Gas
subunit
of
the
heterotrimeric
G
protein
suppresses
the
function
of
Adenylyl
cylase.
(
)
(

1.Bacteriorhodopsin is a protein that has 7 alpha helices embedded in the cell membrane. As such, how many start-transfer and stop-transfer sequences would it need?

7 start transfer sequences, 6 stop transfer sequences

7 of each, in alternating fashion

4 start transfer sequences and 3 stop transfer sequences

7 start transfer sequences

2. The role of GTP hydrolysis by the Signal Recognition Particle during cotranslational translocation to the ER is

to release the SRP after docking to the translocon so translation can resume.

to open the gate/pore of the translocon into the ER.

to arrest translation so that synthesis does not finish before the peptide is delivered to the translocon.

to allow binding to the ribosome.

3. The cisternal maturation model is just one model that describes how objects might move through the Golgi. Some of the statements below describing the cisternal maturation model are correct and some are incorrect. Select all the incorrect descriptions.

There's no need for retrograde movement

Vesicles bud off from the Trans Golgi Network toward the plasma membrane

Vesicular tubules move materials from the cis to medial Golgi networks.

There are no vesicles moving in the anterograde direction

4. Select all statements that are correct concerning electron transport and ATP synthesis during photosynthesis in chloroplasts.

Each photosystem (I and II) pump protons.

Protons are pumped into the lumen of the thylakoid.

The bulb of the synthase projects into the stroma

Photosystem I is reduced directly by Photosystem II

5. Select all that are true about ATP synthesis with an FoF1 synthase complex.

Each ADP+Pi is transferred from one beta subunit in Open conformation to a second beta subunit in Loose conformation and finally to the 3rd beta subunit in the T conformation

As the gamma subunit rotates to each beta subunit, it forces them to the open state.

As the gamma subunit rotates to a particular beta subunit, the unit before it changes conformation to Tight and the one ahead of it changes to Loose

As the gamma subunit rotates to a particular beta subunit, the unit before it changes conformation to Loose and the one ahead of it changes to Tight

All 3 beta subunits are always in a different conformation (open, loose, or tight)

6. The number of ATPs per NADH generated by the electron transport system is higher than the number generated per FADH2 because __________.

electrons from FADH2 are not oxidized all the way to water

NADH is converted to NAD+, which increases the charge gradient for ATP synthesis

FADH2 has a lower (less negative) redox potential than NADH does

FADH2 has a higher (more negative) redox potential than NADH does