Lecture 18: Protein Lipidation Flashcards
(98 cards)
1
Q
protein lipidation (def.)
A
a covalent modification of proteins by lipids
2
Q
protein lipidation can play a key role in _____ and _____ of modified protein
A
localization and function
3
Q
most modifications are ___ but some can be ____
A
stable (permanent)
dynamic (regulated addition and removal)
4
Q
protein lipidation promotes localization in membrane by ____
A
acting as an anchor in membrane
5
Q
protein lipidation can be ___ or ____
A
co-translational
post-translational
6
Q
Five main categories of Protein Lipidation
A
1) glypiation
2) cholesteroylation
3) prenylation
4) Acylation
5) Other
7
Q
glypiation is the addition of _____
A
GPI anchor
8
Q
cholesteroylation is the addition of _____
A
cholesterol
9
Q
prenylation is the addition of _____
A
farnesyl and geranylgeranyl
10
Q
acylation is the addition of _____
A
fatty acids (myristate and palmitate)
11
Q
other types of protein lipidation is the addition of _____
A
phospholipids
12
Q
several proteins are subject to _____ because it promotes _____
A
multiple lipidation
strong association with membrane
13
Q
nature of lipidation affects ___ and ____
A
localization and properties
14
Q
5 main lipids
A
1) myristate
2) palmitate
3) palmitoleic
4) farnesyl
5) geranylgeranyl
15
Q
protein lipidation with myristate linkage? to associated residue? stability?
A
amide/H2N-Gly –> stable
16
Q
protein lipidation with palmitate linkage? to associated residue? stability?
A
thioester/cysteine –> dynamic
amide/ H2N-Cys –> stable
17
Q
protein lipidation with palmitoleic linkage? to associated residue? stability?
A
oxyester/serine –> stable
18
Q
protein lipidation with farnesyl linkage? to associated residue? stability?
A
thioether/cysteine –> stable
19
Q
protein lipidation with geranylgeranyl linkage? to associated residue? stability?
A
thioether/cysteine –> stable
20
Q
2 saturated lipids
A
1) myristate
2) palmitate
21
Q
3 unsaturated lipids
A
1) palmitoleic
2) farnesyl
3) geranylgeranyl
22
Q
cholesterol can be ___
A
inserted into membrane
23
Q
protein cholesteroylation helps with ____
A
protein insertion into membrane
24
Q
main targets for protein cholesteroylation are ___
A
protein of the Hedgehog family (Hh)
25
Hedgehog protein family (def.)
family of secreted signaling proteins needed for growth and patterning
26
Hedgehog protein family are morphogens that can ____
elicit developmental fate over significant
distances
27
Hedgehogs are produced as ______ and large extension at ______
larger precursors with signal sequence
the C-terminus
28
Hedgehogs require ____
extensive processing
29
Cholesteroylation of Hh proteins method
1) cleavage in conserved Gly-Cys-Phe (GCF) on C-terminus after translocation
2) auto-processing mediated by C-terminal extension
3) Transfer of cholesterol to C-terminal glycine
4) Stable palmitoylation at N-terminus on Cys
30
Both the _____ and _____ (protein lipidation) are essential for function of Hh proteins
cholesteroylation
stable palmitoylation
31
the protein modifications of Hh proteins allows the ____
secreted signaling domain to remain tethered to PM
32
the protein modifications of Hh proteins help the protein to form____
micelles
33
Protein isoprenylation occurs on _____
cysteine residue part of the “-CAAX” or “-CXC” motifs at the C-terminus
(A-aliphatic residues)
34
Protein isoprenylation forms ___ bond
Irreversible thioether
35
Isoprene has how many carbons?
5
36
Farnesyl residue has how many carbons?
15
37
geranylgeranyl residue has how many carbons?
20
38
General rule: when to add geranylgeranyl vs farnesyl residue?
-geranylgeranyl: CAAX, CXC --> X = leucine (L)
- farnesyl: anything else
39
the synthesis pathway of cholesterol contains ____
many lipids used in protein lipidation as intermediates
40
Protein isoprenylation of small GTPases is needed for ___
attachment to membrane
41
Geranylgeranylated proteins display ____affinity for membranes (especially ___)
high
di-geranylgeranylated proteins
42
geranylgeranyl group is _____ than farnesyl group
10-40X more hydrophobic
43
Some prenylated proteins (____) must be extracted from membranes by ____
Rabs
specialized chaperones (GDIs, Guanine nucleotides dissociation inhibitors)
44
GDI keeps protein bound to ___
GDP
45
fatty acylation with ___ and ____ acts to mediate ____
myristate and palmitate
special types of membrane targeting
46
fatty acylation uses how many types of fatty acids?
3; all saturated but of different lengths
47
3 types of fatty acids for fatty acylation
- C8:0, octanoate (ghrelin etc…)
- C14:0, myristate
- C16:0, palmitate
48
fatty acylation increases protein ___ and promotes _____
hydrophobicity
weak membrane interaction
49
myristate (# carbons?)
14
50
palmitate (# carbons?)
16
51
____% of human proteome is myristoylated
~0.5%
52
N-myristoylation adds ____
myristate co-translationally to N-terminal
glycine
53
enzyme needed for N-myristoylation?
- N-myristoyl transferase I (Nmt I)
54
Nmt I is associated with ___
ribosome
55
Nmt I transfers ___ following removal of ____
myristate
initiating methionine
56
N-myristoylation bond formed?
amide bond
57
N-myristoylation stability?
Stable (not reversible)
58
N-myristoylation often works with ____ to regulate membrane association
second signal
59
S-Palmitoylation is typically added _____ to _____
post-translationally to thiol group of specific cysteine residue
60
S-Palmitoylation stability?
Reversible, dynamic
61
Most common lipid modification
Protein Palmitoylation
62
S-Palmitoylation is easily detectable because ____ which is cleavable with ____
it involves a thioester bond
hydroxylamine
63
S-Palmitoylation is typically used to ____
regulate protein function
64
S-Palmitoylation happens what type of protein?
many different types of proteins
65
S-Palmitoylation happens on what residue? near what?
usually Cys residue close to membrane surface, sometimes near myristoyl or prenyl group
66
proteins with this domain acts as palmitoyl acyltransferases (PATs) in many organisms?
DHHC-domain (zDHHC containing proteins)
aspartate-histidine-histidine-cysteine
67
Glypiation occurs when? stability? targets? function?
-post-translational
-stable
- extracellular proteins
- targets proteins to rafts
68
Cholesteroylation occurs when? stability? targets?
-post-translational on newly exposed C-terminal glycine
-stable
- found on members of hedgehog family
69
Isoprenylation occurs when? stability? targets? function?
- post-translational on cysteine within -CAAX, -CCAAX or -CXC
-stable
-promotes membrane recruitment and further processing
70
-N-palmitoylation occurs when? stability? targets? function?
- post-translational on N-terminal cysteine
- found on members of hedgehog family
- stable (amide bond)
71
-N-myristoylation occurs when? stability? targets? function?
- co-translational on N-terminal glycine of cytosolic protein
- stable (amide bond)
72
*S-palmitoylation occurs when? stability? targets? function?
-post-translational on cysteine, various positions
- thioester bond cleavable with hydroxylamine
- reversible/dynamic (thioester bond)
73
Cancer cells often increase the expression of _____
N-myristoyltransferase
74
PCLX-001 treatment results in _____
the degradation of N-myristoylated proteins
75
PCLX-001 selectively ____
kills blood cancer cells in vitro
76
PCLX-001 induces cells death by _____
triggering apoptosis
77
composition of lipids in organelles depends on ___
what organelle it is?
78
Synthesis of lipid is ____ in the cells.
location-specific
79
Final steps in the synthesis of phospholipids (eg. PC) are catalyzed by _____
membrane-bound enzymes on the cytosolic surface of the endoplasmic reticulum
80
Cholesterol synthesis is completed _____
on the ER membrane
81
Addition of headgroups to ceramide to produce glycosphingolipids (sugar) or sphingomyelin (choline) occurs ______
on the lumenal face of cis and trans-Golgi membranes
82
Trans-bilayer movement (flip-flop) of charged lipids is _____ in artificial liposomes
extremely slow
83
Generation of Membrane Asymmetry at ER membrane
Phospholipids synthesized on cytosolic side of ER membrane are transferred to lumenal leaflet by a scramblase (maintains
equilibrium across bilayer)
84
Membrane Asymmetry at ER membrane? ATP?
ATP independent
85
Scramblase at PM action? stimulated by? ATP?
-moves lipids in both directions
-simulated by calcium
-ATP independent
86
movement of amino-phospholipids at PM action? stimulated by? ATP?
- PS and PE moved from outer to inner leaflet by specific flippase
-creates asymmetry
-ATP dependent
87
floppase works at ___ and is responsible for ____
PM
export of lipids from the cell
88
floppase action? ATP?
moves phospholipids from inner to outer leaflet at PM
ATP hydrolysis promotes activity
89
floppase best characterized as a member of ______ protein family
ABC (ATP-binding cassette)
90
Membrane asymmetry critically controls _____
transmembrane protein function
91
Movement of ____ from the ______ to other
compartments relies on ______
sphingolipids
Golgi complex
vesicle-mediated transport
92
Phospholipids and cholesterol can move between organelles by ______
different mechanisms that do not involve vesicles
93
Phospholipids and cholesterol movement to cell surface? speed? ATP?
extremely rapid movement to cell surface
- ATP-independent
94
drug that block COPI function
BFA
95
transport of phospholipids and cholesterol is not eliminated by ____
BFA (drug that blocks COPI - vesicle transport)
96
mechanism for transport of phospholipids and cholesterol involves____
Lipid Transfer Proteins (LTPs)
97
proteins CERT and ORP5 do what?
create unique interorganelle contact sites to facilitate exchange of specific lipids
98
phospholipids, ceramide and cholesterol transport involves ___ and/or ______
specific transfer proteins
inter-organelle membrane contact sites (MCS)
