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BIOL 266 PROTEINS > Unit 6 > Flashcards

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
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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
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3
Q

TOM40

A
  • Composes general import pore of outer mitochondrial membrane
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4
Q

TIM23 & TIM17

A
  • Compose import pore of inner membrane
  • Proteins pass through this import pore at contact sites between inner & outer membrane
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5
Q

TIM44

A
  • Binds to Hsc70
  • ATP hydrolysis by this complex helps power translocation of the protein in the matrix
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6
Q

Membrane-bound ribosomes

A
  • Attached to cytosolic surface of ER membrane & are synthesizing proteins that are translocated into the ER
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7
Q

Free ribosomes

A
  • Unattached to any membrane & are synthesizing all of the other proteins
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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
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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
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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
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11
Q

Signal peptidase

A
  • ER membrane
  • Protease
  • Cleaves signal sequence of protein allowing rest of protein to synthesize into ER lumen
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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)
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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)
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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)
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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)
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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

BIOL 266 PROTEINS (12 decks)

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