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Molecular Biology Test II - Jourdan > Intracellular Compartments and Protein Sorting 1 > Flashcards

Intracellular Compartments and Protein Sorting 1 Flashcards

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0
Q

What is a nucleus?

A

Principal site for DNA and RNA synthesis

Contains the genome

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1
Q

What is a plasma membrane?

A

Outer boundary of cells, and a bilayer

It is a protective barrier with transporters and signaling

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2
Q

What is cytoplasm?

A

Consists of cytosol and cytoplasmic organelles

And is an intermediary metabolism

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3
Q

What is Endoplasmic Reticulum ER?

A

Ribosomes attach to the rough ER and the smooth ER has no ribosomes
It is a place for proteins synthesis, lipid synthesis, protein folding, and storage of calcium

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4
Q

What is the golgi apparatus?

A

Stacks of disc-like compartments

-post-translational changes on proteins and lipids occur here and also trafficking

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5
Q

What does the mitochondria do?

A

Makes ATP, signaling, cell differentiation and cell death.

Has an outer and inner membrane and matrix

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6
Q

What are lysosomes?

A

The digestive system of the cell: contain digestive enzymes that degrade organelles and biomolecules

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7
Q

What are peroxisomes?

A

Small vesicular compartments that contain enzymes used in oxidation reactions

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8
Q

what 3 topological categories does the cell divide into?

A

Nucleus and cytosol
Organelles in secretory and endocytic pathways
Mitochondria

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9
Q

How does the nucleus and cytosol communicate?

A

Through nuclear pore complex. Topologically they are the same and one organelle

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10
Q

What are organelles in secretory and endocytic pathways?

A

ER, Golgi, Endosomes, and lysosomes

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11
Q

How do organelles in secretory and endocytic pathways communicate?

A

Through vesicles

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12
Q

What allows topologically equivalent organelles to communicate with each other and with the cell exterior?

A

Membrane budding and fusion allows the lumen of each of these compartments to communicated

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13
Q

What are the types of protein trafficking?

A

Gated transport
Transmembrane transport
Vesicular transport

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14
Q

What type of protein trafficking is between the nucleus and cytosol through nuclear pore complexes?

A

Gated transport

Active transport and free diffusion

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15
Q

What is transmembrane transport?

A

Membrane proteins translocators directly transport specific proteins from cytosol across an organelle membrane

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16
Q

What is vesicular transport?

A

Membrane-enclosed transport intermediates that move proteins between various compartments via vesicles

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17
Q

What guides protein transfer/transport to various compartments?

A

Sorting signals

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18
Q

What are sorting signals?

A

Stretch of amino acids, typically 15-60 residues long

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19
Q

Where may sorting signals be localized?

A

On N or C terminus or within the protein sequence

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20
Q

What forms a signal patch?

A

Multiple scattered sequences in protein may form signal patch

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21
Q

What may remove the signal after protein reaches final destination?

A

Signal peptidase

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22
Q

Signal sequences are both necessary and sufficient for ____________

A

Protein targeting

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23
Q

What is more important than actual sequence in a sorting signal?

A

Physical properties of the sequence (e.g. charge, hydrophobicity)

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24
Q

What are signal sequences recognized by?

A

Complementary receptors

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25
Q

Describe nuclear transport?

A

Gated, bidirectional, and selective

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26
Q

What proteins are needed in nucleus?

A

Histones, DNA and RNA polymerases, topoisomerases, and gene regulatory proteins

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27
Q

Where are proteins needed in the nucleus imported from?

A

The cytoplasm where they are synthesized

28
Q

What proteins are synthesized in the nucleus and exported to cytosol?

A

tRNA and mRNA molecules

29
Q

What are nuclear pore complexes?

A

(NPCs) Perforate nuclear envelope in eukaryotes

30
Q

What is the molecular mass of NPCs?

A

About 125 million Da

31
Q

What is the NPC composed of?

A

30 different proteins or nucleoporins

32
Q

What is the arrangement of NPCs?

A

Octagonal symmetry with one or more aqueous pores

33
Q

How many NPCs does the nuclear envelope have?

A

3000-4000 NPCs

34
Q

What direction does the NPCs transport molecules?

A

Both directions

35
Q

What type of transport do NPCs do?

A

Passive diffusion of small molecules and facilitated transport

36
Q

What is transport facilitated by in NPC?

A

Binding of particles to fibrils extending from NPC

37
Q

What are Nuclear localization signals?

A

(NLS)
Sorting signals that direct molecules to nucleus
Short sequences rich in positively charged amino acids lysine and arginine

38
Q

What are NLS located on? What do they form?

A

Many different sites on protein and form loops or patches on surface

39
Q

What do NLS result in?

A

Selective import of proteins into nucleus

40
Q

What are NLS recognized by?

A

Nuclear import receptors (NIRs)

41
Q

What does each NIR recognize specifically?

A

A subset of cargo proteins

42
Q

What are NIRs?

A

Soluble cytosolic proteins that bind to NLS on protein and to NPC proteins present on fibrils that extend into cytoplams

43
Q

What do NPC proteins have? What is their purpose?

A

Phenylalanine glycine (FG) repeats which serve as binding sites for import receptors

44
Q

How do receptors plus its cargo traverse NPC?

A

By binding, dissociating, and re-binding to adjacent FG repeats

45
Q

What happens once the cargo passes the NPC?

A

It is released inside the nucleus and NIR returns to cytoplasm

46
Q

What types of binding occurs with nuclear import receptors?

A

Direct binding with 3 different cargo proteins

and indirect binding via adaptor protein

47
Q

What is nuclear export?

A

Works similar to import but in opposite direction. It transports cargo out of the nucleus

48
Q

What does nuclear export rely on?

A

Nuclear export signals (NES) on molecules that need to go out of the nucleus

49
Q

What receptors are needed?

A

Need complementary nuclear export receptors (NER)

50
Q

What does NER bind to?

A

Cargo present in nucleus and NPC proteins

51
Q

What facilitates transport during nuclear export?

A

Binding, dissociation and re-binding

52
Q

Where is the cargo released during nuclear export?

A

Into cytoplasm

53
Q

What drives nuclear transport in appropriate direction?

A

Gradient of Ran conformational states

54
Q

How does the import receptor and cargo enter the nucleus?

A

By interacting with FG repeats on NPC proteins

55
Q

What binds to complex of import receptor and cargo?

A

Ran-GTP

56
Q

What does the binding of Ran-GTP to complex of import receptor and cargo cause?

A

The release of cargo

57
Q

What leaves the nucleus after cargo is released in the nucleus?

A

Ran-GTP and import receptor

58
Q

What happens to Ran-GTP in the cytoplasm?

A

It is hydrolyzed by Ran-GAP and the receptor is released from the Ran-GDP (hydrolyzed ran-gtp) and is ready for another cycle

59
Q

Some proteins contain both ____ and _____

A

NLS and NES

60
Q

Where do proteins with both NLS and NES shuttle back and forth?

A

Between nucleus and cytosol

61
Q

What does the steady state localization dependent upon?

A

Relative rate of transport

62
Q

If rate of import is greater than export, ________

A

It is considered nuclear, and vise versa

63
Q

What can the changing rate of import/export change?

A

Location of protein

64
Q

Gene regulatory proteins transport is _________

A

Stringently controlled

65
Q

What is kept out of nucleus until needed?

A

Gene regulatory proteins

66
Q

Gene regulatory protein transport is controlled by what?

A

By NLS and NES being turned on and off

67
Q

What mechanisms are used to turn on and off the NLS and NES on gene regulatory proteins?

A

Phosphorylation, proteolysis, and binding to inhibitory proteins

Molecular Biology Test II - Jourdan (9 decks)

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