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BIOL2210 cell signalling and membrane > llecture 4 > Flashcards

llecture 4 Flashcards

1
Q

what does the signal peptidase recognise

A

small neutral side chains

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2
Q

what drives the movement across the ER

A

Sec63+BiP also HSP

ahs peptide binding domain and ATPases domain.

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3
Q

what does Sec63 promote

A

BiP-ATP hydrolysis. makes change so it can bind to polypeptide chain.

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3
Q

how does type 1 integral membrane protein insert into the membrane

A

hydrophobic TM domain enter translocon. the stop-transfer anchor sequence take place. once embedded translocation continues.

N-terminal ER sequence is cleaved. C-terminal is cytosilic

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3
Q

how is type 2 membrane protein inserted

A

located internally. SRP recognises it. TM domain is signal sequence. embeds in ER bilayer.

c-terminal is luminal

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4
Q

describe type 3 membrane insertion protein

A

same as type 2. positive charge placement is different on C-terminal side so C-terminus is in cytosol. has internal signal sequence can’t’ cleave.

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5
Q

give and example for type1,2,3

A

1= LDL receptor, insulin receptor, growth hormone receptor

2= transferin receptor

3= cytochrome 450

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6
Q

what do tail anchored membrane proteins depend on

A

Get3(ATPase) binds to c-terminal of protein. Get1/Get2 receptor recruits. ATP hydrolysis. c-terminus release and embedded

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7
Q

describe the topology of type 5 membrane protein

A

alpha helix direct, anchor or stop transfer protein to ER. N-terminus can be cytosolic or luminal.

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8
Q

what attaches phospholipid anchors to proteins

A

glycosylphosphatidylinositol which is a amphipathic molecule

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9
Q

what recognises the AA sequence near N-terminus

A

transamidase

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10
Q

what does transamidase do

A

cleave stop anchor sequence. transfer ER luminal part to GPI membrane anchor.

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11
Q

what modifications take place in the ER

A

N-linked glycosylation

disulphide bond formation

aid folding

oligomer formation

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12
Q

what modifications take place in the golgi

A

o-linked glycosylation

proteolytic processing

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13
Q

what modification takes place at the cell surface

A

protein shedding

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14
Q

describe how n-linked glycosylation takes place

A

glycan+ nitrogen atom of asparagine= oligosaccharide- nascent polypeptide in lumen of ER- cleave pyrophosphate bond between dolichol-glycan molecule. processing reactions. glucose and mannose removed. n-linked glycan- ER chaperones+ 3 glucose residues on core. help fold. 3 glucose removed. if fold fail + 3 glucose.

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15
Q

how do disulfide bonds form in secretory proteins

A

oxidising environment. link sulfhydryl groups. 2 cysteine residues. not in cytosolic protein. protein disulphide isomerase present. reducing agent. Ero 1- carries s-s bond to give to PDI. oxidise PDI. disulphides exchange on protein.

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16
Q

describe protein oligomer formation

A

spikes form hemagglutinin protein. trimers formed in ER of host cell. =precursor HA0.post translational.

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17
Q

what do o-glycosyltransferases do

A

+ activated sugars to O-atom on serine and threonine residues

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18
Q

describe the proteolytic processing

A

inactive to functional. basic AA pairs recognised by endoproteases in golgi.

19
Q

what does proteolytic shedding do

A

=soluble membrane proteins.

20
Q

give an example of proteolytic shedding

A

ADAM family remove ectodomains of membrane proteins

21
Q

what sequence does the KDEL-R recognise

A

KDEL

22
Q

which retention signal reaches the plasma membrane

A

Kir6.2 RKR

22
Q

what mediates golgi targeting

A

transmembrane domains hydrophobic. 17-25 AA long

22
Q

what are cytosolic motifs

A

golgi targeting signal. 4-10 AA. charge residue interact with cytosolic factor and machinery

23
Q

give an example of a cytosolic motif and what it does

A

SDYQRL. tyrosine interact with adaptor complexes. AP2 u2 binds to tyrosine motif. captures TGN46 at plasma membrane goes back to golgi network

24
Q

what is AP1-5

A

clathrin associated adaptor protein complex. recognise tyrosine and dileucine base signal

25
Q

what is GGA1-3

A

located in golgi. trafficks cargo from TGN to endosome system

25
Q

describe the clathrin triskelion

A

3x clathrin heavy chains 3x light
adaptor complexes bind to clathrin help in tis self assembly and recruitment.

26
Q

what do vesicle coats bind to

A

sorting signals

26
Q

what does sec24 recognise

A

di-acidic motif at ER COPII

27
Q

what is dynamin GTPase

A

neck of vesicle- polymerise- energy GTP- change- neck stretches- pinches off

28
Q

what happens when GTP hydrolysis doesn’t take place

A

the clathrin bud cannot pinch off

29
Q

what drives the depolymerisation of the clathrin coat

A

HSP70

30
Q

what disrupts mitochondrial targeting

A

mutation of hydrophobic and hydrophillic residues on either side of the helix

31
Q

what do import receptors recognise

A

Tom 20 and 22 both on outside of mitochondrial membrane

32
Q

what keeps proteins in disaggregated state

A

HSP70 AND 90

33
Q

what is Tom 40

A

import pore for unfolded chain. passive driving force comes from matrix.

34
Q

what does Tom 40 associate with

A

Tim23 and 17 which HSP70 interacts with via Tim44 when entering . both drive the polypeptide into the matrix

35
Q

describe the mitochondrial inner membrane protein pathway A

A

Tom20/22-N-terminal sequence-Tom40-inner membraneTim23/17- sequence cleave- hydrophobic stop transfer sequence-translocation stop-insert membrane

36
Q

describe pathway B

A

matrix targeted-internal hydrophobic domain-Oxa1 recognises it.

37
Q

describe pathway c

A

internal sequence-Tom70/22-trnaslocated-Tim22/54-transfer-Tim9/10-chaperones-stop folding-Tim22/54 insert hydrophobic regions into membrane.

38
Q

how are outer mitochondrial membrane proteins arranged

A

beta barrel-all interact with Tom40 and go to sorting and assembly complex

39
Q

what does SAM consist of

A

3 proteins

40
Q

how were nuclear localisation signals discovered

A

by large T-antigen of simian virus 40

41
Q

give an example of peroxisome targeting

A

PTS1+ Pex5-Pex14 in membrane peroxisome-catalase released to interior- through Pex2/10/12-folded proteins translocated

42
Q

how are peroxisomes generated

A

Pex3 and 16-ER membrane-recruit Pex19-bud off-empty peroxisome

BIOL2210 cell signalling and membrane (11 decks)

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