Intracellular compartments and protein sorting 1 (lecture 10) Flashcards
1
Q
What is the Plasma membrane
A
- Outer boundary of cells,bilary
- fxn: protective barrier, has transporter, signaling
2
Q
Nucleus
A
- Contains the genome
- principle site for DNA and RNA synthesis
3
Q
Cytoplasm
A
- Consists of cytosol and cytoplasmic organelle
- intermediary metabolism
4
Q
Enoplasmic Reticulum (ER)
A
- Ribosomes attached to it (rough ER), no ribosomes (smooth ER)
- Protein synthesis, lipid synthesis, protein folding, storage of calcium
5
Q
Golgi apparatus
A
- Stacks of disc-like compartments
- site of post-translational changes on proteins and lipids, trafficking
6
Q
Mitochondria
A
- Outer and inner membrane and matrix
- Makes ATP, signaling, cell differentiation and cell death
7
Q
Lysosomes
A
- Contain digestive enzymes that degrade organelles and biomolecules
8
Q
Peroxisomes
A
- Small vesicular compartments that contain enzymes used in oxidation reactions
9
Q
What intracellular compartment makes up the majority of the cell
A
Cytosol
10
Q
The cell can be divided into what 3 topological categories
A
- Nucleus and cytosol (communicate through nuclear pore complex)
- Organelles in secretory and endocytic pathways (ER, Golgi apparatus, endosomes, and lysosomes) (communicate through vesicles)
- Mitochondria
11
Q
Nucleus and cytosol communicate through _____ complex
A
- nuclear pore complex
12
Q
Organelles in secretory and endocytic pathways (ER, Golgi apparatus, endosomes, and lysosomes) communicat through
A
Vesicles
13
Q
membrane ____ and ____ allows the lumen of the cell compartments to communicate with each other and with the cell exterior
A
Budding and fusion
14
Q
Protein trafficking
A
- Gated transport
- Transmembrane transport
- Vesicular transport
15
Q
Gated transport: between ____ and ___ through nuclear pore complexes (active transport and free diffusion)
A
Nucleus and cytosol
16
Q
Transmembrane transport: membrane _______ directly transport specific proteins from cytosol across an organelle membrane
A
Protein translocators
17
Q
Vesicular transport: membrane-enclosed transport intermediates move proteins between various compartments via
A
vesicles
18
Q
Protein transfer/transport to various compartments guided by ____
A
sorting signals
19
Q
Sorting signals on proteins are a stretch of amino acids, typically ____ residues long
A
15-60
20
Q
Sorting signals may be localized on ___ or ___ terminus or _____
A
N or C terminus, within protein sequence
21
Q
A
22
Q
multiple scattered sequences in protein may form
A
signal patch
23
Q
____ may remove signal after protein reaches final destination
A
signal peptidase
24
Q
Protein signal sequences are both necessary and sufficient for _____
A
protein targeting
25
\_\_\_\_\_\_\_\_\_ properties of the protein signaling sequence are more important than the actual sequence
physical properties (charge,hydrophobicity)
26
Protein signal sequences are recognized by \_\_\_\_\_\_
complementary receptors
27
what is the protein signal sequence for importing into nucleus
* Pro-Pro-Lys-Lys-Lys-Arg-Lys-Val
* (note that there are 5 positive charges)
28
Nuclear transport is \_\_\_\_, _____ and \_\_\_\_\_
gated, bidirectional, and selective
29
Proteins needed in nucleus (e.g. histones, DNA and RNA polymerases, topoiserases, gene regulatory proteins) are imported from ____ where they are synthesized
cytoplasm
30
\_\_\_\_ and ____ molecues synthsized in nucleus are exported to cytosol
tRNA and mRNA
31
Nuclear pore complexes (NPCs) perforate ____ in eukaryotes
Nuclear envelope
32
What si the moleuclar mass of nuclear pore complexes (NPCs)
125 million Daltons
33
Nuclear Pore Complexes (NPCs) are composed of ____ different proteins or \_\_\_\_-
30, nucleoporins
34
Nuclear Pore coplexes (NPCs) are arranged in \_\_\_\_- symmetry with one or more \_\_\_\_\_\_
ocagonal symmetry, aqueous pores
35
Nuclear envelope has ______ Nuclear pore comlexes (NPCs)
3000-4000
36
Nuclear Pore Complexes transport molecules in \_\_\_\_\_\_
both directions
37
Nuclear pore complexes (NPCs) transport molecuels in both directions. By means of ____ of small molecules and \_\_\_\_\_
Passive diffusion, facilitated transport
38
Nuclear pore complexes (NPCs) faciliate tansport by
binding of particles to fibrils extending from NPC
39
\_\_\_\_ are sorting signals that direct molecules to the nucleus
* Nuclear Localization Signals (NSL)
40
Nuclear localization signals (NLS) are short sequences rich in _____ amino acids ____ and \_\_\_\_
postitivley charged amino acids lysine and arginine
41
Nuclar locatlization signals (NLS) are located on many different sites on protein- form ____ or ____ on surface
loops or pathes
42
Nuclear Localization Signals (NLS) result in ____ import of proteins into nucleus
selective
43
Nuclear localization signals (NLS) are recognized by
nuclear import receptors (NIRS)
44
Nuclar import receptors (NIRs) are ______ that bind to ____ on protein and to ______ present on fibrils that extend into cytoplasm
soluble cytosolic proteins, NLS, NPC proteins
45
NPC proteins have _____ which serve as binding sites for import receptors
Phenylalanine glycine (FG) repeats
46
Nuclear import receptors plus cargo traverse NPC by \_\_\_, \_\_\_, and ___ to adjacent Phenylalanine glycine (FG) repeats
binding, dissociating, and re-binding
47
Once cargo is released inside the nucleus the NIR
return to cytoplasm
48
Nuclear import receptors (NIRs) can either do ____ binding or ____ binding to cargo protein with help of adapter protein
direct or indirect binding
49
Nuclear export works similar to import but
in opposite direction
50
Nuclear export relies on _____ on molecules that need to go out of nucleus
nuclear export signals (NES)
51
For nuclear export Nuclear export signals (NES) on molecules need complementary
nuclear export receptors (NER)
52
NER binds to cargo present in nucleus and ____ proteins
NPC
53
Gradient of ____ conformational states drive nuclear transport in appriate direction
Ran
54
RAN-GTP binds to complex of ____ and \_\_\_\_. The binding causes release of cargo. Ran-GTP and ____ then leave the nucleus and return to cytoplasm. In the cytoplasm Ran-GTP is hydrolyzed by \_\_\_\_\_. The _____ is released from Ran-GDP and is ready for another cycle
import receptor and cargo, import receptor, Ran-GAP. Import receptor
55
Shuttle protein contain both ____ and \_\_\_. This allows them to shuttle back and forth between ___ and \_\_\_
NLS and NES. nucleus and cytosol
56
Steady state locatlization is dependent upon
relative rate of transport
57
If the rate of import is greater than export, the shuttle protein is considered \_\_\_\_
nuclear
58
Gene regulatory protein can regulate transport by turning ____ and ____ on and off. The mechanisms include \_\_\_\_, \_\_\_\_, and \_\_\_\_\_\_
NLS and NES. phosphorylation, proteolysis, and binding to inhibitory proteins
59
Feedback regulation of cholesterol biosynthesis
SREBP (sterol response element binding protein), a latent transcription regulator that controls expression of cholesterol biosynthetic enzymes, is initially synthesized as an ER membrane protein. It is anchored in the membrane by interaciton wiht another ER memabre protein, called SCAP (SREBP cleavage activation protein), which binds cholesterol. If the cholesterol binding site on SCAP is empty (at low cholesterol concentrations), SCAP changes conformation and is packaged together with SREBP to free its cytosolic domain form the membrane. The cytosolic domain then moves into the nucleus, where it binds to the promoters of genes that encode proteins involved in cholesterol biosynthesis and activates their transcription. In this way, more cholesterol is made when its concentration falls below a threshold.
