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BGM2002 > l10 > Flashcards

l10 Flashcards

1
Q

give three examples of reactive oxygen species

A

H2O2, superoxide anion 02-, hydroxyl radicals OH

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2
Q

What are the cellular sources of reactive oxygen species (ROS)

A

ETC in mitochondria and NAPDH oxidase complex by phagocytes

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3
Q

What is ixidative stress?

A

ROS level > antioxident capacity of the cell

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4
Q

What can be oxidatively damaged by ROS?

A

proteins, lipids and DNA

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5
Q

What are the things that occur as a result of o2 damage of proteins liids and DNA?

A

apoptises, cell death, cancer, ND, diabetes, agening

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6
Q

What is the free radical of aging?

A

aging occurs as a result of accummulation of oxidantion

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7
Q

What are the endogenous sources of O2 in cells?

A

mitochondria, peroxisomes, NAPH oxidase

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8
Q

What are the exogenous sources of ROS?

A

UV, chemotherapy, env. tociins and ionising raidation

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8
Q

What are the antioxidant defences

A

Enzymatic (CAT SOD) and non-enxymatic (gluytathionine)

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8
Q

What are the two sonesquences from ROS that could result in againg

A

impaired physiological fn and accumulation of O2 damage

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8
Q

Are all ROS harmful?

A

not necesaruly

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8
Q

What sort of things can protein oxidation signal for in cells?

A

Growth, division, migration, differentiatio

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8
Q

what’s the key amino acid when it comes to protein oxidation

A

cysteine

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8
Q

What can the oxidation of thiols regulate?

A

protein function, activity and cellular localisation

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8
Q

What is the side chain in cysteine?

A

thiol (SH)

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9
Q

Does sulphenic acid make disulphide bonds? If yes, why, and if so is it the only thing it forms

A

Yes. Sulphenic acid very reactive. No. Forms two types of disulphide bonds (intra and inter) and forms sulphenamide (S-NH)

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9
Q

What is the product of thiol being exposed to low levels of H2O2?

A

sulphenic acid (one thiol (SH), one S-OH)

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9
Q

What happens when sulphenic acd is further oxidised

A

Turns into sulphinic acid (S=O,OH)

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9
Q

What can the ocidation of sulphenic acid be reversed by? What type of molecule is this?

A

thrioredoxin, Trx. Protein

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10
Q

Is sulphenic to sulphinic acid reversible

A

yes, srx.

11
Q

What determines the specificity of protein oxidation

A

uncommon acid, not as accessible, and only a few are redox sensitive.

12
Q

Why are only few cystine residues redox sensitive

A

depends on pKa

13
Q

What is pKa?

A

pH at which 50% of pop. de-protonated

14
Q

What is the common pKa value of most protein thiols?

A

8

15
Q

What is the pH of cells?

A

7

16
Q

What is the redox sensitive thiols pKa?

A

3-5.5

17
Q

How do we get redox sensitive thiol groups?

A

neighbouring AA - needs to be close to proton accepting AA, His, lys, Arg.

18
Q

How does thioredoxin reduce oxidised cystine residues?

A

using electrons from NADPH

19
Q

How is oxidised thioredoxin reduced?

A

thioredoxin reductase

20
Q

How does thioredoxin reductase reduce oxidised thioredoxin?

A

electrons from NADPH

21
Q

How does srx12 reduce cysteine-sulphinic acid

A

ATP - dep

22
Q

What is the issue with oxidation as a PTM?

A

unstable as breaking open cells = artificial o2.

23
Q

What is the solution to the artificial oxidation of proteins?

A

acid lysis, lowers pH of the cell so cystiene residues remain protonated. and cysteine0binding chem. only bind to reduced custeine residues

24
Q

How are intermolecular disulphides detected?

A

DTT - reducing agent, reduces disulphide bonds

25
Q

oxidation detected by an increase in _____ and is ____ sensitive

A

size, DTT

26
Q

What is the issue w western blotting and DTT?

A

what’s the interacting partner & we need specific Ab

27
Q

What are cystine binding chemicals

A

only bind to reduced cysteine residues

28
Q

what are the three cystine binding chemicals and MW

A

NEM - 0.1 kDa block cyst. residues

AMS, 0.5 kDa

PEG-Mal 2-5 kDa

  • protein interaction ?
29
Q

why are proteins from cells extracted under acidic conditions

A

avoid artificial oxidation

30
Q

How is disulphide interactions noted?h

A

No AMS will bind to the disulphide bond

31
Q

How does AMS binding affect mobility on SDS page?

A

heavier MW, slower

32
Q

What are the advantages of using SDS page

A

visualise protein oxidation by mobility change

33
Q

What are the issues in using SDS PAGE?

A

Type of oxidation is not revealed and again specific antibodies are needed

34
Q

What do we use to detect intramolecular disulphide

A

PEG-Mal

35
Q

How do we detect intraM disulp. bonds?

A

Block SH groups with NEM, reduce using DTT, and then label using PEG-Mal.

36
Q
A
36
Q
A
36
Q
A
37
Q

What’s the issue with disulph. bond detection

A

is the cysteine res. modified? need specific Ab/

BGM2002 (6 decks)

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