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Cell Bio > Week 2 > Flashcards

Week 2 Flashcards

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1
Q

What do heat shock protiens do

A

Serve to protect cells from diverse phsyical and chemical insults

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2
Q

Who discovered heat shock response

A

Ferruccio Ritossa

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3
Q

What happened in the heat shock discovery

A

Inccaubator was turned up and chromatin puffs form heat induced activation of gene transcrption localized in that specific regions of the cchromosomes

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4
Q

What temperature are heat shock protiens triggered by

A

Just a few degrees

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5
Q

What are some examples of changes in cell morphology and organization

A

Remodelling cytoskelton,
fragmentation and disassemble of the golgi and ER, swelling of the nucleoli

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6
Q

What happens in the fibroblasts of a chinese hamster that is treated with hyperthermia

A

Disruption of the fine structure of the actin filaments but stabilization of the cell cortex (MORE ROUNDED)

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7
Q

What are the 7 classes of proteins for cells to cope with stress

A

Chaperons
DNA/RNA repair
Metabolic enzymes
Regulatory proteins
Proteolytic system
Transport and detoxification
Cell organization

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8
Q

What are chaperons

A

Specific proteins that interact with, stabilize or help other protiens to acquire its functionally active conformation without being present in its final structure

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9
Q

What do RNA and DNA enzymes

A

Necessary to repair DNA damage and processing failures that occur during stress

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10
Q

What are metabolic enzymes

A

Needed to reorganize and stabilize the energy supply of the cell

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11
Q

What are regulatory protiens

A

Transcrption factors or kinases needed to further initiate stress response pathways or to inhibit expression cascafes

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12
Q

What is the proteolytic stystem enzymes

A

Needed to clear misfolded and irreversibly aggregated protiens from the cell

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13
Q

What are cell organization proteins

A

Required in sustaining cellular structures such as the cytoskeleton

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14
Q

What are transport and detoxifying proteins for

A

needed to maintain or restore membrane stability and function

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15
Q

What can detect up-regulation of heat shock protein

A

Western blot technique

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16
Q

What else is important for protein folding pathway

A

Chaperone HSPS like HSP70

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17
Q

What is the oil drop model

A

Some proteins are capable of self-assembly into a single stable conformation hydrophobic inside hydrophilic outside

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18
Q

Where do chaperones bind

A

Hydrophobic patches to prevent misfolding

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19
Q

Do chaperons determine by the three dimensional state

A

NO amino acid sequences does chaperons just helps them get there

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20
Q

What are the five chaperone families

A

Hsp100
Hsp90
Hsp70
Hsp 60
sHsps

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21
Q

What chaperone family is energy independent

A

sHSPs

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22
Q

What are the two general families of chaperones

A

Molecular chaperones and Chaperonins

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23
Q

What are molecular chaperones

A

Proteins that bind and stablize unfolded proteins, and facilitate their folding through exposed peptide sequences of hydrophobic amino acids prevent them from aggregating

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24
Q

What are chaperonins

A

Ring shaped chaperons that form small folding chambers that encapsulate non native protiens in an ATP dependent manner

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25
Q

What is the structure of Hsp100

A

Two hexametric ring complexes with a channel

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26
Q

How does Hsp100 work

A

By actively pulling misfolded protiens through a central chanel using ATP which is then unfolded

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27
Q

What happens once the protien is relased from HSP100

A

it can refold properly

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28
Q

Is Hsp100 in humans

A

NO

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29
Q

What organisms encode HSP90

A

Everything except archea

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30
Q

What are the five subfamiles of HSP90

A

Cytosolic
ER
Chlorplast
Mitochondrial TNFR
Bacterial high temperature

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31
Q

What are the three domains of Hsp90

A

N-terminal ATP binding domain
Middle domain
C-terminal domain

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32
Q

What does Hsp90 always funciton as

A

Dimer

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33
Q

What is the process of ATPase of Hsp90

A
  1. Inactive substrates binds to the middle domain when the chaperone is in the open confirmation
  2. ATP then binds to the NTD conformational change and closes the lid
  3. After lid closure NTD dimerize and twists
  4. NTD dissociated anre the release of activated substrate (folded protien)
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34
Q

What is Hsp90 known as

A

A sensor of heat shock response

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35
Q

What does Hsp90 inhibit

A

HSF1 transcrptions factors which induces many stress sensitivite genes

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36
Q

What is happening under normal conditions for Hsp 90

A

HSF1 is bound to Hsp90 in the cytoplasama

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37
Q

What happens when the cell is stress in regards to Hsp90

A

accumulation of unfolded protiens occur which comepte for HSF1 but HSF1 binds more readily these monomers rapidly trimerize and transloacte to the nucleuse

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38
Q

What else is required for HSF-1

A

Postranslational modification

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39
Q

How does HSF1 upregulate transcrption of target genes

A

By binding the heat shock element present in the target gene promoters

40
Q

What does induction of heat shock protiens do

A

Inhibits apoptosis and promotes cell survival

41
Q

What is the DBD

A

DNA binding domain it is resposbinsle for binding HSF1 to the shock element N terminal domain

42
Q

What does the trans activation domain do

A

C terminal domain required for binding the transcription factor to the pre-initiation complex

43
Q

What makes up the preinitiation complex

A

RNA polymerase II and general transcption factors

44
Q

What is the regulatory domain responsible for

A

Regulating HSF1 activity

45
Q

How does the Regulatory domain regulate HSF1 in the absence of stress

A

RD restraians the HSF1 TAD negatvie regulation of the trans activating capacity of HSF1

46
Q

What is HR

A

Specific domains called hydrophobic heptad repeat regions mediate oligomerization/trimerization through formation of three stranded coiled-coil structure

47
Q

How is trimerization negatively regulated

A

Intermolecular interactions between the HR-A/B and HR-C domains under non-stress conditions

48
Q

What are heat shock elements

A

Specific sequences in DNA found in genes

49
Q

What is the pentameric sequence

A

Inverted of nGAAn

50
Q

How many repeats serve as a binding site for HSF1 trimer

A

3

51
Q

What is a prominent feature of HSF1 to convert it to a trimer

A

Extensive hyperphosphorylation of serine residues in the RD

52
Q

Can posttranslational modification of HSF1 stimulatory or inihibitory

A

BOTH

53
Q

What is sumolyation

A

Covalent attachment of small SUMO proteins similar to ubiquitin doesn’t direct proteins for degradation

54
Q

What always represses HFS1 activity

A

Phosphorylation-dependent sumolyation that serves as a stress sensititve barrier that restains HSF1 activity upon moderate stress

55
Q

What heat shock protien does not work is association

A

HSF3

56
Q

What else is HSF1 responsible for

A

Immune responses and cancer

57
Q

What are HSF1 and HSF2 known for

A

Developmental process, oogenesis, spermatogensis and corticogensis

58
Q

What is HSF4 involved in

A

Development of different sensory orgrans

59
Q

Exposure of cells to heat shock can be detected by what

A

Fluorescence microscopy

60
Q

Where are nuclear stress bodies found

A

Located close to the nucleoli or nuclear envelope

61
Q

What was used to detecet HSF1

A

monoclonal antibodies

62
Q

Where are HSF1 and HSF2 found

A

Co-localized

63
Q

What are Hsp70 and Hsp90 known as

A

Foldases

64
Q

What are some properties of Hsp70

A

Highly conserved
Located in many organelles
Stress inducible
ATP dependent
Function as a monomer
Regulated by two co-chaperones

65
Q

What are the two domains of Hsp 70

A

N terminal nucleotide binding domain
C terminal substrated binding domain (SBD)

66
Q

What does the NBD bind too

A

ATP and hydrolyzes it to ADP

67
Q

What is the SBD divided into

A

Beta-sheet base and an alpha helical lid

68
Q

What is the lid consit of

A

5 helices A-E

69
Q

What follows the SBDa

A

Unstructured region

70
Q

What happens when Hsp70 is ATP bound

A

The SBD-a is open and peptides bind and release realtivitly rapidly there is a low affinity with the help of HSP40

71
Q

What is BiP

A

Principal Hsp70 chaperone of ER stress in the ATP bound state

72
Q

What happens with the hydrolysis of ATP in HSP 70

A

Accelerated by HSP40 closes the a-helical lid and a tight binding of substraate by HSP70 (high affinity) proper protien folding is facilitated

73
Q

What happens once the protien is folded correctly by Hsp70

A

Dissociation of ADP and binding of ATP by NEF to have the open confirmation

74
Q

What are chaperonins

A

Large double ring complex and form barrel shaped structures with two folding chambers

75
Q

What are group 1 chaperonins

A

Have 7 subunits in each ring expressed in bacteria, mitochondria and chlorplasts and cooperate with Hsp10 protiens which form the lid of the cage

76
Q

What are examples of Group 1 chaperonins

A

Hsp60 in eukaryotes and GroEL in bacteria

77
Q

What are group II chaperonins

A

Expressed in archaea and the eukaryotic cytosol and have 8-9 subunits in each ring and no lid is required so independent of Hsp10

78
Q

Can each 7 subunit bind ATP

A

YES

79
Q

What are the four steps of chaperonin-mediated protien folding

A
  1. Mis-folded protein is captured by hydrophobic residues near the entrance of the upper folding chamber (the lower chamber is blocked by the lid)
  2. ATP binding then induces a conformational change of the chamber that triggers the GroEL lid to seal the upper chamber containing the encapsulated protien
  3. Protien folding in chamber due to ATP hydrolosis once it is hydroloyzed another ATP can bind and a new lid binds to the other chamber
  4. The binding causes the lid to dissociate from the upper chamber and release the folded protien
80
Q

What is the highly conseverd domain in sHsp

A

ACD

81
Q

What does the ACD structurally composed off

A

Beta sandwhich of two anti baraelle sheets of three or four beta strands

82
Q

What else might ACD do

A

Mediate strong protein interactions and contribute to oligomerization of sHsps

83
Q

Do sHsp domains contain ATP binding site

A

NO

84
Q

What are the other domains of sHsps and are they important

A

NTR and CTR and yes for oligomerization and function

85
Q

What are sHsps been orginally termed as

A

holdases as they bind and hold many unfolded proteins

86
Q

What type of recations work with sHsp

A

Hydrophobic interactions

87
Q

Is it a spontaneous recation of refolding non-native protiens in sHsp

A

NO you need the cooperation of ATP-dependent chaperones

88
Q

What does the current model suggest

A
  1. sHsps populate at equilibrium a wide variety of inter-converting oligomers
  2. Under stress conditions substrate proteins are destabilized and being to unfold
  3. The sHsp ensemble becomes activated by remodelling the large ensemble in favor of smaller oligomers with more substrate binding sites
  4. Activates sHsps bind unfolded protiens in an energy-independent manner
  5. sHsp/substrate complexes are stabilized in different forms
  6. Bound substrates may recative spontaneously or are refloded by the ATP dependent Hsp70 chaperone system
89
Q

What else can sHsps do

A

Matian the stability of actin filaments under stress conditions

90
Q

The regulation depends of actin depends on what

A

phosphorylation of sHss which occuers under stress condtions

91
Q

What happens to actin in unstressed cells

A

unphosphorylated sHsps monomers (HSBP1) cap the plus end so it doesn’t polymerizaie

92
Q

What happens to actin in stressed cells

A

sHsps are phosphorylated lareg oligomers are dissocated and phosphorylate sHsps bind to the surface of actin filaments and protect them from depolymerization and aggregation

93
Q

What chaperones are in E.coli

A

Hsp60 (GroE), Hsp70, sHsps and Hsp90 Hsp100

94
Q

What chaperones are in S.cerevisiae

A

Hsp70 sHsps, Hsp100,HSP 90 Chaperonins are abundant under phsiological conditions but downregulated in heat stress

95
Q

What is present in A.fulgidus

A

The chaperone system up-regulated upon heat shock consists only of sHsps and Hsp60

96
Q

What is present in H.sapiens

A

Hsp70 Hsp90 sHsps are upregulated Hsp60 is not Hsp100

Cell Bio (13 decks)

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