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Arrrgggggh Flashcards

1
Q

What are the ER flippases?

A

Energy independent

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2
Q

What are an example of energy dependent inward flippases?

A

PA P-type flippases

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3
Q

What are an example of energy dependent outward flippases?

A

ABC transporters

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4
Q

What proteins are transported by signal based targeting?

A

Soluble and membrane proteins

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5
Q

What type of proteins are transferred by vesicles?

A

Integral membrane proteins

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6
Q

Describe N-terminal signal sequences.

A

16-30 residues long with 6-12 hydrophobic amino acids and one or more positive amino acids at the N-terminal

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7
Q

Describe the SRP.

A

6 proteins bound to 300nt of RNA including a p54 segments that is hydrophobic and binds the hydrophobic amino acids of the signal sequence.

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8
Q

What does the SRP bind to?

A

The large ribosomal unit and the signal sequence

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9
Q

What residues may be present where the signal peptidases cleaves?

A

A,C, G, T at -1 and -3

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10
Q

What does the Sec63/BiP complex do?

A

BiP is a heat shock protein that is located in the ER lumen and it binds to GTP and, when GTP is hydrolysed by Sec63 then the BiP changes conformation and can bind to the incoming polypeptide helping to chaperone it and prevent it from sliding back into the translocon.

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11
Q

What is topology of the membrane?

A

How many times the polypeptide spans the membrane

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12
Q

What is type I integral proteins?

A

Cleanable N-terminus, C-terminal is cytosolic and N-terminal is luminal. Stop transfer anchor sequence

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13
Q

What is type 2 integral proteins?

A

No cleavage N-terminus, C-terminal is luminal and N-terminal is cytosolic. Positive charges on the N-terminal side.
Internal signal anchor sequence

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14
Q

What is type III integral proteins?

A

N-terminal not cleavable and luminal, C-terminal cytosolic but positive residues on the C-terminal side.
Positive charges are Cytosolic

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15
Q

What are type IV integral proteins?

A

Have more than one membrane spanning transmembrane domain

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16
Q

What are type V membrane proteins?

A

Sequences near the stop anchor sequence are recognised by a transamidase that cleaves then and then allows the protein to move to a lipid anchor (GPI etc.)

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17
Q

What is the two types of bond for N-linked glycosylation?

A

Glycosidic - between sugar molecules (carbons 1 & 4)
Between the protein and the sugar (Asn-X-Ser/Thr)
X cannot be proline

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18
Q

What is the precursor molecule made up of and built up on?

A

3 glucose, 2 GlnNac, 9 mannose

Dolichol - transferred by oligosaccharide transferase

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19
Q

What catalyses disulphide bond formation and what brings S-S to this protein?

A

PDI and EroS

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20
Q

Describe hemagglutinin formation.

A

Monomers of HA are made and transferred to the membrane. Interaction of there monomers initially by alpha helices forms a trimer

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21
Q

What does peptidyl-propyl isomerise do?

A

Rotates the peptide bond on proline to change it from a cis to a trans

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22
Q

What is BiP in yeast?

23
Q

What does ubiquitous ligase E3 recruit?

A

E2 - ubiquitous conjugating enzyme that adds ubiquitin to K48

24
Q

What sugars does O-linked glycosylation use?

A

Already activated sugars: CMP and UDP

Linked to oxygen or serine or threonine

25
What is proteolytic processing?
The conversion of an inactive form to an active one (protein). Base pair of amino acids are recognised by specific endonucleases - RR, KR, KK RK
26
What is shedding?
Catalysed by the ADAM family - conversion of a protein into a soluble protein. Proteolytic removal of extracellular domains of many membrane proteins
27
What is myristoylation?
Addition of myrisotyl to the aside nitrogen of asparagine. Irreversible & very stable (same as the protein) Consensus sequence is: -Met-Gly-X2-X3-X4-X5 X2 can't be aromatic, proline or charged X5 can be serine, threonine, glycine, alanine, cysteine or Asn
28
Where does palmitoylation occur?
C-terminus on a cysteine residue | Enhances hydrophobicity
29
What roles does palmitoylation have?
Trafficking between membrane compartments | Ras proteins, insulin receptor, rhodopsin and Fyn kinase
30
What adds and removed Palmitate?
S-palmitoyltransferases and palmitoylthioesterases
31
What are the two types of prenylation?
Geranylgeranyl (C20) and farnesyl (C15) Consensus sequence for F: C-A-A-X Consensus sequence for G: CC or CXC
32
What are the examples of prenylated proteins?
Rab, ras, g-protein gamma subunit
33
What do Ras proteins do?
Proliferation, transmitting signals
34
What do rab proteins do?
Membrane traffic, vesicle formation, vesicle movement and cytoskeleton effects
35
What transports rab to the membrane?
Rab escort proteins that bind the prenyl groups on the two cysteines
36
What are the types of ER signal seqeunces?
KDEL (BiP and PDI) | KKXX, KXKXX, RKR
37
Describe mitochondrial matrix signal sequences.
20-50 residues long Lysine and arginine rich Lots of positive charges Rich in hydrophobic amino acids
38
How do proteins get into the matrix?
Tom 20/22 Tom 40 Tim 44/Tim17/23
39
What is the signal sequence of peroxisomes and what is it recognised by?
SKL Pex5 soluble carrier protein Pex14 - receptor in peroxisome membrane
40
Describe the NLS
7 residues consisting of lots of basic residues
41
Describe the NES
4 hydrophobic residues
42
What does COPII transport from and to?
From the ER to the Golgi | COPI is the reverse
43
What does dynamin do?
Family of severing membrane machines
44
What does API do?
Transport between TGN and endosomes
45
What does AP3 do?
Protein trafficking to lysosomes
46
What shape is clathrin?
Triskelion shaped protein that has three light and three heavy chains
47
What does transferrin recycle?
Iron binds to it and is transported into the cell through endocytosis Iron is released when the pH lowers
48
Describe the LDL receptor
Late endosomes or lysosomes | LDL is degraded and the receptor is recycled
49
What happens to the EGFR?
Degraded or recycled
50
Where is caveolin found?
Lipid rafts | Slower than clathrin mediated endocytosis
51
What are lipid rafts insoluble to?
Triton X-100
52
What happens in macropinocytosis?
The actin cytoskeleton is rearranged and can fold back on itself forming ruffles that then fuse to the plasma membrane and trap solutes and soluble substances in the macropinosomes
53
What lipid are in lipid droplets?
Triglyceride and cholesterol esters

Membranes And Signalling (2 decks)

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