Unit 6 Flashcards
1
Q
Hsc70
A
- Keep mitochondrial import precursor proteins in an unfolded state
- Cytosolic chaperone
- Requires energy in the form of ATP
- Binds to TIM44
- ATP hydrolysis by this complex helps power translocation of the protein in the matrix
2
Q
TOM20 / TOM22
A
- Receptor in outer mitochondrial membrane
- Interacts with matrix-targeting sequence in protein
- Transfers protein to general import pore of outer membrane
3
Q
TOM40
A
- Composes general import pore of outer mitochondrial membrane
4
Q
TIM23 & TIM17
A
- Compose import pore of inner membrane
- Proteins pass through this import pore at contact sites between inner & outer membrane
5
Q
TIM44
A
- Binds to Hsc70
- ATP hydrolysis by this complex helps power translocation of the protein in the matrix
6
Q
Membrane-bound ribosomes
A
- Attached to cytosolic surface of ER membrane & are synthesizing proteins that are translocated into the ER
7
Q
Free ribosomes
A
- Unattached to any membrane & are synthesizing all of the other proteins
8
Q
SRP
A
- Signal recognition particle
- Cytosolic side of ER cytoplasm
- Composed of 6 proteins & an associated RNA molecule
- Engages emerging polypeptide that has its ER signal sequence exposed
- Binding halts translocation & delivers ribosome / polypeptide to ER
9
Q
SRP receptor
A
- ER membrane (Cytosolic surface)
- Ribosome / polypeptide delivered here by SRP
- This interaction is enhanced by binding of GTP to both SRP & its receptor
10
Q
Translocon
A
- ER membrane
- Ribosome / polypeptide delivered here during ER import
- This induces it to open & receive a polypeptide (enters as a loop)
- Hydrolysis of GTP by SRP & its receptor free these for another round of import
- Translocation resumes
11
Q
Signal peptidase
A
- ER membrane
- Protease
- Cleaves signal sequence of protein allowing rest of protein to synthesize into ER lumen
12
Q
Type I membrane-anchored protein
A
- Single-pass
- Cleaved signal sequence at N-terminus
- Uses SRP-SRP receptor to get to ER membrane
- N(out)-C(in)
13
Q
Type II membrane-anchored protein
A
- Single-pass
- No cleavable signal sequence
- Uses SRP-SRP receptor to get to ER membrane
- N(out)-C(in)
14
Q
Type III membrane-anchored protein
A
- Single-pass
- No cleavable signal sequence
- Uses SRP-SRP receptor to get to ER membrane
N(in)-C(out)
15
Q
Tail-anchored membrane-anchored protein
A
- Signal-pass
- No cleavable signal sequence
- Hydrophobic membrane-spanning sequence at C-terminus
- Does not use SRP-SRP receptor, but the GET 1/2/3 system to get to ER
- Post translational insertion
- N(in)-C(out)
16
Q
Type IV membrane-anchored protein
A
- Multispanning
- No cleavable signal sequence
- Uses SRP-SRP receptor for insertion of the first membrane-spanning domain but not subsequent ones
- IV-A are N(in)-C(in)
- IV-B are N(out)-C(in)
17
Q
GPI-anchored membrane-anchored protein
A
- Entire protein is lumenal (out)
- Cleaved signal sequence at N-terminus
- Uses SRP-SRP receptor to get to ER membrane
- Anchored at C-terminus to membrane & then transferred to GPI anchored
18
Q
Get3
A
- Binds to hydrophobic tail in tail-anchored membrane-anchored proteins when in its ATP-bound state
- Hydrolyses ATP & releases the polypeptide once bound to Get 1/2 complex, embedding its hydrophobic stretch into the ER membrane
- Binds ATP & is released from membrane, ready for another round of activity
19
Q
Get 4/5 & Sgt2
A
- Bind hydrophobic tail at tail-anchored membrane-anchored protein before it binds to Get3
20
Q
Get 1/2 complex
A
- Binds to Get3 complex of ER membrane
21
Q
GPI-anchored proteins
A
- Insert into ER like type I membrane-anchored proteins using a STA sequence
22
Q
Transamidase
A
- Cleaves protein within lumen of ER & transfers it to assembled GPI anchor
23
Q
Clathrin
A
- Mediates transport vesicle formation at the trans-golgi (for transport to lysosomes via endosomes) & at the plasma membrane (for transport to endosomes)
24
Q
COP I
A
- Mediates transport from cis-golgi to ER & between various Golgi cisternae
25
Q
COP II
A
- Mediates transport from ER to cis-Golgi
26
Q
Sar1
A
- Rab protein
- Activated by its GEF
- Inserts into membrane & begins to curve membrane
- Activated Sar1 recruits inner coat portion of COP II coat made up of proteins Sec23 & Sec24
27
Q
Sec23 & Sec24
A
- Further bends ER membrane
- Sec24 acts as cargo receptor for membrane proteins
- Recruit outer layer of COP II coat made up of proteins Sec13 & Sec31
28
Q
Arf1
A
- Rab protein
- Activates, & along with a COP I complex forms COP I coat at Golgi
29
Q
Multiprotein tethering complexes
A
- Composed of up to 10 proteins
- Localize to distinct organelles
30
Q
Coiled-coil proteins
A
- Long α-helical proteins that project great distances from target membrane
31
Q
SNARE proteins
A
- Mediate Docking
- v-SNAREs on vesicle
- t-SNAREs on target membrane
- Over 35 SNARE proteins
- Have SNARE motif, allowing it to interact with another SNARE protein
32
Q
trans-SNARE-complex
A
- When vesicle is docked, SNAREs associate as a bundle of α-helices called 4-helix bundle
- 3 helices contributed by t-SNARE proteins, & 1 contributed by v-SNARE protein
- On 2 distinct membranes
- Energy released after SNARE pairing sufficient to bring membrane & vesicle close together & disperse the water around polar heads
33
Q
NSF
A
- Hexameric ATPase
- Attaches to cis-SNARE complexes using accesory proteins (SNAP proteins)
- ATP hydrolysis breaks apart stable cis-SNARE complexes & allows SNARES to be reused in another round of fusion
34
Q
Dynamin
A
- Small GTP-binding protein
- Aids in breaking clathrin coated vesicle free from plasma membrane
- Using GTP-hydrolysis, it breaks vesicle free from plasma membrane
