Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ANAT 212 > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

how do cells respond to stress that causes protein misfolding

A

increasing expression of chaperones and other specialized proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

are all chaperones hsps

A

NOOO
but all hsps are chaperones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

describe hsr

A

heat shock response = cytosolic and nuclear proteins, protects against cell death

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

describe upr

A

unfolded protein response =ER proteins, can promote cell death if stress too severe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what do cells tailor the expression of chaperones to

A

tailor amount of chaperones to need of cell that has to reform misfolded proteins
the level of unfolded and misfolded protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

describe inducible chaperones

A

heat shock proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

describe constitutive chaperones

A

assisted protein folding = proteins that facilitate folding of others = hold or stabilizing hydrophobic residues and assist folding
universal mechanism of protein homeostasis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

describe drosophila and heat

A

heat induces transcription activation of certain genes and expression of specific proteins
discovered by accident
all cells respond to heat the same way = stop producing some proteins and favour production of other proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is heat shock response activated by

A

unfolded cytosolic proteins - heat stress or oxidative damage or proteasome inhibition of alcohol ingestion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what happens during and after stress

A

during = transcription of hsps upregulated and transcription of other genes = down regulated - many hsps are chaperones
response continues after stress removed to help cells recover
expression highest ~12 hrs after = need time to refold proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what does HSF1 do

A

activates transcription of hsps

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

describe HSF1

A

transcription factor mediates hsr
has dna binding domain, regulatory domain, transcription activation domain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

describe active and inactive HSF1

A

inactive HSF1 = monomeric
active hsf1 = trimer = recognizes HSE (heat shock element) promoters
trimerizes = quaternary structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

describe regulation of hsf - step 1

A

monomeric hsf1 is folded but mimics unfolded protein and is bound by hsp90
hsp 90 holds as monomer - recognizes patches

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

describe regulation of hsf - step 2

A

after heat shock unfolded proteins compete with hsf1 for hsp90 binding = more proteins want hsp90 so leaves hsf1 and allows hsf1 to trimerize and bind promoter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

describe regulation of hsf - step 3

A

free hsf1 trimerizes and activates transcription

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

describe regulation of hsf - step 4

A

chaperones including hsp 90 are expressed and help fold or degrade unfolded proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

describe regulation of hsf - step 5

A

hsf1 is down regulated by binding of excess hsp90 to the monomer form
so hsf1 is now bound again

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

do all substrates need the same chaperones

A

NOOOO
certain degrees of specificty
some substrates require specific chaperones or combos of chaperones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

describe atp dependent chaperones

A

Actively promote folding
substrate binding and release are regulated by atpase cycles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

describe atp independent chaperones

A

prevent aggregation and can catalyze some folding steps
good at holding substrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

describe cooperation between chaperones

A

usually work in network
cytosol
endoplasmic reticulum
constitutive and inducible = create network for the cell to have all the proteins folded

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

describe families of chaperones

A

Different families of chaperone proteins use various biochemical mechanisms – “protein folding toolkit”
3 families of ATP-dependent chaperones, with different structures and ATPase cycles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

name atp dependent chaperone families and describe briefly

A

hsp 70 = works as monomer
hsp90 = dimer, nutcracker
chaperonines = hsp60 = provides cage and safe environment for protein to fold by itself

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

describe hsp70 - table

A

cytosol = hsc70 (active) and hsp70 (inducible)
ER = BiP
others = mitochondria, ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

describe hsp90 - table

A

cytosol = hsp90, alpha and beta
er = GRP94
others = mitochondria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

describe hsp60- table

A

chaperonin
cytosol = TRic
er = -
others = hsp60 in mitochondria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what does hsp60 function like

A

E coli GroEL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

which chaperones are constitutively expressed

A

all are always expressed except HSP70

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

which chaperones are induced by heat shock response

A

hsp70
hsp90
hsp60

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

which are induced by ER unfolded protein response

A

Bip
GRP94

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

describe hsp70 family

A

70kda monomers
atpase domain controls substrate binding domain of hsp70
atp bound = no substrate binding
adp bound = substrate binding domain is closed tightly on peptide
binds short hydrophobic sequences

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

how does hsp70 function

A

with help of cochaperones = proteins which contact chaperones to regulate activity
some can bind to polypeptide substrates themselves and are both chaperones and cochaperones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

name hsp70 co-chaperones

A

DNAJ (HSP40) family promote hsp70 substrate binding
nucleotide exchange factors
(NEFS) promote substrate release

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

describe hsp70 functional cycle - step 1

A

hsp40 recognzies misfolded protein
Hsp40-mediated delivery of substrate to ATP-bound Hsp70
induces atpase activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

describe hsp70 functional cycle - step 2

A

Hydrolysis of ATP to ADP mediated by Hsp40 results in closing of the α-helical lid and tight binding of substrate by Hsp70
conformational change = allows hsp70 to bind substrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

describe hsp70 functional cycle - step 3

A

NEF catalyzes exchange of ADP for ATP
adp liberates and binds to hsp70

38
Q

describe hsp70 functional cycle - step 4

A

Opening of the α- helical lid, induced by ATP binding, results in substrate release

39
Q

describe hsp70 functional cycle - step 5

A

Released substrate either folds to native state
or given to another hsp

40
Q

describe DNAJ co-chaperones

A

regulate hsp70 function
many = at least 53 genes in humans

41
Q

describe domains of DNAJ co-chaperones

A

all have conserved j domains = bind transiently to hsp70, activate it to hydrolyze atp (induces atpase activity) and bind polypeptide, DOES NOT bind substrate
other domains determine their specific biological function = could bind substrate or for trimerization

42
Q

which DNAJs are the most highly conserved

A

substrate binding dnajs

43
Q

describe substrate binding dnajs

A

j domain, substrate binding, dimerization
homodimers = 2 subunits of 40-50kda (originally identified as hsp40)
bind short hydrophobic sequences
transfer substrate to hsp70 during atp hydrolysis

44
Q

describe dnajs that bind substrate

A

some bind substrate through specific domains and act as atp independent chaperones
like HSP40
can hold and help fold

45
Q

describe dnajs that do not bind substrate

A

specific domains attach dnaj to protein complex or intracellular membrane
these recruit hsp70s to complex or membrane - bring to complex that has substrate

46
Q

describe NEFs

A

Nucleotide Exchange Factors (NEF) remove ADP from HSP70 and allow ATP to bind
NEF binding opens up HSP70 ATPase domain and weakens interactions with nucleotide
ATP binds when NEF dissociates
ATP-bound HSP70 to releases polypeptide (transition)
Several NEF families in humans

47
Q

how does hsp70 help folding

A

HSP70 binds hydrophobic regions of folding intermediates and prevents incorrect contacts from forming
Release of polypeptide from HSP70 provides chances for it to fold
Balance between DNAJs and NEFs supports an optimal rate of HSP70 substrate binding and release
Substrate-binding DNAJs may provide additional assistance Can form multi-chaperone complex with HSP90

48
Q

describe hsp90 family

A

homodimers with 2 identical subunits joined at c terminus - human - hsp 90 = 2x90kda=180kda
open and close like nutcracker
atp controls opening and closing
cochaperone p23 = stabilizes closed form
thought to bind polypeptides at late stages of folding –> stabilizes intermediate folded states (specific for hsp90)
substrate bound along sides of subunit
diff substrates can bind to diff sites on sides (unlike hsp70s and chaperonins)

49
Q

describe hsp90 functional cycle - informal

A

n terminus = atp binding domain
c terminus = dimerization domain
dimer
Recognizes client
HOP = cochaperone recognoizes hsp70 and 90
p23 stabilized binding and now closed
atp hydrolyzed
FKBP52
open and cannot bind client

50
Q

describe hsp90 functional cycle - 3 steps

A

1 - Substrate is bound weakly in the open nucleotide-free state
2 - ATP binding allows dimer to close and bind substrate tightly
3 - ATP hydrolysis to ADP compacts the dimer and releases substrate

51
Q

describe hsp70-hsp90 co-chaperone system

A

Cytosolic HSP70 and HSP90 form a multi- chaperone system
cooperate to assist substrates
Substrate is released from HSP70 and bound by
HSP90 in coordination
HOP assists complex formation
HSP70 dissociates when HSP90 binds ATP

52
Q

describe the co-chaperones that regulate hsp 70 and hsp90

A

many cochaperones regulate = sometimes active on substrates, provide flexibility, folding and non folding functions

53
Q

what is similar between hsp70 and hsp90

A

similar eevd motif
cytosolic hsp70 and 90 = not homologous but have similar c terminal sequence motids
4 aas = motif (4-5 recognized by domain)

54
Q

what recognizes EEVD motifs

A

TPR domains recognize eevd motifs
can be specific for hsc70, hsp90 or both

55
Q

describe TPR cochaperones

A

tpr domains are adaptors to hsp70/90
often have other domains which interact with substrates directly

56
Q

name tpr cochaperones

A

HOP
FKBP52
CHIP

57
Q

describe HOP

A

has domains which bind hsp70 and hsp90 specifically
2 tpr domains

58
Q

describe FKBP52

A

has an hsp90 binding tpr domain and PPlase domains (cochaperone and chaperone)
PPlase = peptidyl-prolyl isomerase = chaperone specific to prolines (P52) = proline is cis and trans so domain helps transition of proline from cis to trans

59
Q

describe CHIP

A

binds either hsp70 or 90
has ubiquitin ligase domain that helps degrade proteins = if no way to fold = degrade

60
Q

what are many hsp substrates

A

signal transduction proteins = kinases, receptors, transcription factors
many also require hsc70

61
Q

what can hsp90 bind without needing HSC70

A

hsp90 can bind kinases without needing hsc70

62
Q

what do mutations in signalling proteins cause

A

cancer `

63
Q

what are drug targets for cancer treatments

A

HSP90 and HSC70

64
Q

describe c-src and v-src

A

c-src = cellular, normal kinase involved in signalling cell growth, cells have this, kinase not always active, autoregulated
v-src = viral, mutant kinase that causes cancer, modified so not regulated region = always active and always cell division

65
Q

descibe v-src - drug therapy

A

must inhibit hsp90 = viral kinase won’t achieve native conformation - folded functional state
1 - v-src expressed in epithelial cells causes them to become cancerous
2 - treat cells with hsp90 inhibitors
3 - hsp90 cannot chaperone v-src anymore
4 - cells revert from cancer to normal growth

66
Q

describe hsp60 family

A

large oligomeric complexes with typical double ring structure
2 cages = one up and down, have alternate cycles
depends on what binds = can be a bigger or smaller cage - accommodates substrate differently

67
Q

describe groel cavity

A

rings are identical and work in alternating cycles

68
Q

describe groel cavity - down position

A

no nucleotide
subunits around ring bind to hydrophobic polypeptide
smaller
wall of hydrophobic residues - interact with other residues = cavity will attract misfolded proteins

69
Q

describe groel cavity - up position

A

atp bound
subunits bind to groes cap instead of substrate
large cavity with polar surface formed
Substrate released inside cavity = enclosed but no longer bound
provides space to fold

70
Q

describe groel subunits

A

Each GroEL subunit has an ATPase domain and a substrate- binding domain
The ATPase domain is the interface with the opposite ring (upside down)
Movement of the substrate binding domain is controlled by the ATPase
in both rings
atp bound = conformation change

71
Q

describe groel functional cycle - one ring

A

smaller conformation – bring substrate
conformational change and promotes binding of cap
~7 secs = atp hydrolyzes and proteins folds by itself
then liberate groes, folded protein and adp

72
Q

how does groel help folding

A

Substrate enclosed inside polar cavity
provides chance to fold
confinement promotes folding by favouring more compact conformations
atp hydrolysis acts as a timer for substrate release

73
Q

what functions like groel

A

human mitochondrial HSP60

74
Q

describe human chaperonin in cytosol

A

TRiC (TCP1 ring complex)
does not have cap co-chaperone
long substrate binding domains form the cavity themselves

75
Q

what causes heat shock response - summary

A

stress conditions that trigger protein misfolding induce hsr

76
Q

what does heat shock response refer to - summary

A

activation of expression of certain constitutive and inducible chaperones known as hsps

77
Q

how are hsps identified - summary

A

by molecular weight and atp dependent or independent

78
Q

what do hsps do - summary

A

fold proteins in cytosol and nucleus and are pro-survival

79
Q

describe hsp families - summary

A

3 main atp dependent = hsp90, hsp70, hsp60
use diff approaches and co-chaperones to fold proteins

80
Q

do misfolded proteins usually only need one chaperone - summary

A

many client misfolded proteins need cooperation of several co-chaperones

81
Q

describe groel cycle - step 1

A

top ring binds substrate in down position - no nucleotide

82
Q

describe groel cycle - step 2

A

binds atp and moves up to position = conformational change

83
Q

describe groel cycle - step 3

A

binds groes and encloses substrate inside cavity

84
Q

describe groel cycle - step 4

A

hydrolyzes atp
Substrate stays inside

85
Q

describe groel cycle - step 5

A

release adp, moves down to position, substrate released
native substrate will not be bound again

86
Q

what is a consequence of inhibiting hsp90 for cancer therapies

A

hsp90 keeps hsf1 in monomer = so will lead to many more chaperones (since hsf1 will be in active trimer state ) = more proteins and more heat shock response

87
Q

describe GroEL - hsp60 family

A

2 rings x 7 identical subunits x 60kda = 840kda

88
Q

describe GroES - hsp60 family

A

cap co-chaperone
7 subunits x 10kda = 70kda

89
Q

what are homologs of human mitochondrial HSP60 and HSP10

A

GroEL
GroES

90
Q

what does substrate binding domain of groel bind

A

substrate-binding domain either binds substrate (down, no nucleotide) or GroES (up, ATP-bound)

ANAT 212 (34 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions