Glycosylation and lipidation Flashcards
1
Q
Glycans
A
- covalent, extra-proteinous modifications
- structural/modulatory roles
- diversity of monosaccharides
- produced by Gas
2
Q
GTs
A
either use
- dolichol-phosphate precursors or
- oligosaccharide transferases
3
Q
monosaccharide activation
A
- nucleotide sugars are linked to anomeric carbon via O-glycosidic bond
- releases monophosphate sugar and phosphate group
4
Q
Monosaccharide GT donors
A
- nucleotide diphosphates
5
Q
Glycan transport
A
- monophosphate retrograde antiporters
- lumen flippases
6
Q
N-glycosylation
A
- on Asn nitrogen side-chain
- targets secreted TM/EC domains
- transferred in sequons
7
Q
cis-Golgi
A
- 2x mannose trim
- 1x GlcNac add
- high mannose N glycans
8
Q
median Golgi
A
- 3x mannose trim
- 1x GlcNac addition
- 1x fucose addition
- 1x GlcNac addition
9
Q
trans Golgi
A
- 3x galactose addition
- 3x silica acid addition
- complex, heterogenous glycans
10
Q
N-glycosylation polymorphism in spike
A
- spike = 22 sequons
- stabilises RBD dynamics and recognition
11
Q
O-glycosylation
A
- on Ser/Thr et al.
- targets EC/cytoplasmic domains
- classified on 1st monosaccharide
12
Q
pro-hydroxylation
A
- prolyl hydroxylases
- collagen
13
Q
lys-hydroxylation
A
- Lysyl hydroxylases
- collagen
14
Q
tyr-hydroxylation
A
- glycogenin
- glycogen primer
15
Q
GalNac
A
- initiated in Golgi
16
Q
GalNac transferases
A
- approx 20 types
- generate 8 core glycans
- e.g. IgM1, IgG3 hinge regions, protease protection
17
Q
galactose O-glycosylation
A
- O-glycan polymorphism on glycophorin caused by different GT expression
- IgM recognises during blood transfusion
18
Q
mannose
A
- initiated in ER, completed in Golgi
- alpha-dystroglycan in muscle links exoskeleton to cytoskeleton
19
Q
arabinose
A
- on hydroxyproline in SPPP repeat
- extensins for cell wall expansion
20
Q
GPI
A
- catalysed by GPI transamidase
21
Q
GPI regulation
A
- lipid tail modification
- phospholipase C hydrolyses lipid double tail
22
Q
Example of GPI
A
- Matrix Metallo Proteases
- high in metastatic cancers
23
Q
Palmitoylation
A
- S-acylation on Cys residues
- O-acylation on Ser/Thr
- non consensus motif
- > 2000 proteins per cell
- catalysed by PATs
- palmitoyl-CoA substrate
24
Q
PATs
A
- 23 in mammals
- 23 in plants
- TM, catalytic DHHC motif
- enriched in Golgi
25
Q
Depalmitoylation
A
- acyl-protein thioesterases
- multiple lipid tails per protein
26
Q
Palmitoylation function
A
cargo concentration at cisternal rim
27
Q
Myristoylation
A
- onto N-terminal glycine
- NMTs
- eukaryotic
28
Q
co-translational myristoylation
A
methionine aminopeptidase exposes N-terminal glycine
29
Q
post-translational myristoylation
A
caspase end-protease cleaves protein
30
Q
myristoylation example
A
- BID myristoylation
31
Q
Prenylation
A
- on Cys motif
- C-terminal residue removal
- -COOH methylated by cytoplasmic ER integral proteins
