Zaidi: Protein sorting 1&2 Flashcards Preview

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Flashcards in Zaidi: Protein sorting 1&2 Deck (43)
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1
Q

ER translocator structure

A

Has a water filled pore
Core of translocator made of Sec61 complex
3 subunits with the largest surrounding the central pore
Pore gated by short helix which opens and closes pore

2
Q

Protein transport to various compartments guided by

A

Sorting signals

3
Q

Nuclear pore complexes composed of

A

30 different proteins or nucleoporins

4
Q

Ran-GTP is hydrolyzed in the ______ which causes

A

Hydrolyzed in the cytoplasm, which causes release of receptor and Ran-GDP is ready for another cycle

5
Q

TOM

A

Translocase of the outer membrane
Required for import of all nuclear encoded proteins
Inserts them in the outer membrane

6
Q

ER signal sequence interacts with

A

Specific site within pore which opens it

Also interacts with lipid core of ER membrane

7
Q

Mitochondrial signal sequence location

A

N-terminal and internal signal sequences

8
Q

Binding of SRP to signal peptide causes

A

Pause in translation until peptide is relocated to ER membrane

9
Q

Each nuclear envelope has

A

3000-4000 pores

10
Q

ATP uses in mitochondrial transport

A

Dissociation of cytosolic Hsp 70 outside mitochondria
Dissociation of mitochondrial Hsp 70 inside matrix
Folding of imported protein by Hsp 60

11
Q

SRP wraps around the

A

Large ribosomal subunit

12
Q

Steps in import into outer membrane

A

Pass through TOM complex and enter inter-membrane space
Bind chaperone proteins
Bind SAM complex in outer membrane
SAM inserts and folds them in outer membrane

13
Q

OXA complex

A

Mediates insertion of proteins synthesized in the mitochondria

14
Q

Ran-GTP binds _____ which causes

A

Binds complex of import receptor and cargo, which causes release of cargo

15
Q

Nuclear localization signals (NLS)

A

Short sequences rich in positively charged amino acids lysine and argenine
Direct molecules to the nucleus

16
Q

Nuclear import receptors can bind to cargo both

A

Indirectly or directly

17
Q

What drives nuclear transport in the appropriate direction

A

Gradient of Ran conformational states

18
Q

Structure of mitochondrial signal sequence

A

Positively charged residues cluster on one end and uncharged hydrophobic on the other end to form an amphiphilic alpha helix

19
Q

Precursor proteins entering mitochondria are folded or unfolded

A

Unfolded, this is maintained through interactions with chaperone proteins (Hsp 70 family)

20
Q

2 components of TOM & TIM complexes

A

Receptors for mitochondrial precursor proteins

Translocation channels

21
Q

Transport through nuclear pores facilitated by

A

Binding of particles to fibrils extending from Nuclear pore complex (NPC)

22
Q

The signal sequence is fed into the translocation channel first or last

A

First

23
Q

TIM 23

A

Transports soluble proteins into matrix and helps insert membrane proteins in inner membrane

24
Q

NPC have ______ repeats that serve as

A

Phenyalanine glycine repeats which serve as binding sites for import receptors

25
Q

Transport through TIM depends upon

A

Membrane potential

26
Q

Sorting signals are localized

A

On N or C terminus or within protein sequence

27
Q

Stop transfer signal

A

Additional hydrophobic region in polypeptide stops transfer process before entire polypeptide is translocated

28
Q

Shuttling proteins

A

Contain both NLS and NES, causing them to shuttle back and forth between nucleus and cytosol

29
Q

Signal sequences are ______ and _____ for

A

Signal sequences are necessary and sufficient for protein targeting

30
Q

NLS are recognized by

A

Nuclear import receptors (NIRs)

31
Q

SAM complex

A

Sorting and assembly machinery

Translocates and inserts/folds beta barrel proteins in the outer membrane

32
Q

Gated transport occurs between

A

Nucleus and cytosol through nuclear pore complexes

33
Q

SRP made of

A

6 different polypeptides bound to a single small RNA molecule

34
Q

SRP shape/pocket

A

Rod shaped with large hydrophobic pocket lined by methionines

35
Q

ER signal sequences

A

Vary in amino acid sequence

Have 8+ non-polar AA at its center

36
Q

TIM 22

A

Mediates the insertion of a specific subclass of proteins (e.g. ATP, ADP and Pi transporter)

37
Q

Signal peptidase function

A

Removes signal after protein reaches final destination

38
Q

Nuclear pores are arranged in

A

Octagonal symmetry with one or more aqueous pores

39
Q

Most mitochondrial proteins are encoded in

A

Nuclear DNA (although some are made in mitochondria)

40
Q

NIRs puls cargo traverse NPC by

A

Binding, dissociating and rebinding FG (phenylalanine glycine) repeats

41
Q

Pores function in both x and y types of diffusion/transport

A

Passive diffusion

Facilitated transport

42
Q

ER signal sequence guided to ER membrane by what two components

A

Signal recognition particle (SRP)

SRP receptor

43
Q

NIRs are

A

Soluble cytosolic proteins that bind NLS on protein and NPC proteins on fibrils that extend into cytoplasm