PMT Flashcards

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1
Q

What is central dogma?

A

The idea genetic information flows in one direction. The idea that DNA is transcribed into RNA then the RNA is translated into a protein.

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2
Q

What is the post translational modification (PTM)?

A

Covalent addition onto/cleavage of protein after protein biosynthesis.

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3
Q

What is the importance of PTM?

A

Important component of cell signalling.
Increases diversity of proteins.

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4
Q

The main example of why PTM is important?

A

Pluripotent Stem Cells (PSC).

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5
Q

What are pluripotent stem cells (PSC)?

A

Cells which are able to self renew and differentiate into 1 of 3 groups.

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6
Q

What are the 3 groups that PSC can differentiate into?

A
  • Endoderm
  • Mesoderm
  • Ectoderm
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7
Q

What are endoderms?

A

They form gastro-internal and respiratory tracts.

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8
Q

What are ectoderms?

A

Make up skin and nervous system.

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9
Q

What are mesoderms?

A

Germ layer present in animal embryos which later become highly specialised cells.

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10
Q

How is PTM linked to peuripotent stem cells?

A

The direction and destination of these cells is controlled at a PTM level.

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11
Q

What are the different types of PTM?

A

Hydroxylation
Methylation
Lipidation
Acetylation
Disulphide Bond
SUMOylation
Ubiquitination
Glycosylation
Phosphorylation

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12
Q

What is phosphorylation?

A

Adds a phosphate to serine, threonine or tyrosine.

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13
Q

What is glycosylation?

A

Attaches a sugar, usually to an “N” or “O” in an amino acid side chain.

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14
Q

What is ubiquitination?

A

Adds ubiquitin to lysine residue of a target protein for degradation.

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15
Q

What is a SUMOylation?

A

Adds a small protein SUMO (small ubiquitin-like modifier) to a target protein.

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16
Q

What is a disulphide bond?

A

Covalently links to “S” atoms of two different cysteine residues.

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17
Q

What is acetylation?

A

Adds an acetyl group to an N-terminus of a protein or at lysine residue.

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18
Q

What is lipidation?

A

Attaches a lipid, such as a fatty acid, to a protein chain.

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19
Q

What is methylation?

A

Adds a methyl group, usually at lysine or arginine residues.

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20
Q

What is hydroxylation?

A

Attaches a hydroxyl group (OH-) to a side chain of a protein.

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21
Q

How does cleavage promote insulin production?

A
  1. Translation and translocation
  2. Folding, oxidation and signal peptide cleavage
  3. ER export, Golgi transport vesicle packaging
  4. Protease cleavage liberates C-peptide
  5. Carboxypeptidase E produces mature insulin.
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22
Q

What is translocation?

A

Movement of an item from one place to another.

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23
Q

Why is phosphorylation important?

A

1/3 of cellular proteins go through this.
Reversible.
Causes conformational change in the protein.
Activate or deactivate an enzyme.
Carries a 2 neg charge so allows for high energy storage.

24
Q

What are protein kinases?

A

Knocks ATP to ADP.
Proceeds to add phosphate to protein.

25
Q

How may types of protein kinases?

A

513
478 are of homologous catalytic domain (ePK).
35 are atypical

26
Q

Where do phosphates come from?

A

Enzyme catalyse the removal of a phosphate group from a substrate by hydrolysing phosphoric acid monoesters into a phosphate ion and a molecule with a free hydroxyl group (dephosphorylation).

27
Q

What types of phosphates are there?

A

They can be specific or broad range.

28
Q

What are broad range phosphate controlled by?

A

They are controlled by regulatory proteins, often in a chain, cell signaling.

29
Q

What are the functions of glycosylation?

A
  • help correct folding
  • increase protein stability (particularly significant in secreted proteins)
  • cell-cell / cell-environment adhesion
  • Immune response
  • Hormone activity
  • Embryonic development
30
Q

What is the carbohydrate group typically built up on during glycosylation?

A

Dolichol.

31
Q

What is dolichol?

A

Long chain, unsaturated, isoprene units terminating in an a-saturated isoprenoid group, containing an alcohol functional group.

32
Q

What is the N-linked bond in glycosylation?

A

Glycan bind to the amino group of asparagine.

33
Q

What is the typical location for N-linked glycosylation?

A

ER

34
Q

What are some examples of N-linked glycosylation?

A

Insulin receptor
ECM
Regulation

35
Q

What is O-linked glycosylation?

A

Monosaccharides bind to the hydroxyl group serine or threonine.

36
Q

What is the typical area for O-linked glycosylation?

A

ER
Golgi
cytosol
nucleus

37
Q

What are some examples of O-linked glycosylation?

A

Collagen
Pathogenic bacteria
ECM

38
Q

What is the glypiation glycosylation?

A

Glycan core links a phospholipid and protein.

39
Q

What are some examples of glypiation glycosylation?

A

Anchor cell surface proteins.

40
Q

What is the C-linked glycosylation?

A

Mannose binds to the indole ring of tryptophan.

41
Q

What are some C-linked glycosylation examples?

A

Only mammalian cells
ECM

42
Q

What is phosphoglycosylation?

A

Glycan binds to serine via phosphodiester bond.

43
Q

Where does the acetyl group come from in acetylation?

A

Donated by acetyl co-enzyme A.

44
Q

What variations are there in different acetylation reactions?

A
  • Can be enzymatic or non-enzymatic
  • enyzmes involve Acetylase or Deacetylase
  • co- or post-translational modification
45
Q

What is N-terminal acetylation?

A

Co-transitional modification in eukaryotes, it synthesises localisation stability.

46
Q

What is lysine acetylation?

A

Often the cycle is linked to transcription factors and it is used for activation of gene expression.

47
Q

What is a NAT?

A

N-terminal acetyltransferases catalyses the N-terminal acetylation.

48
Q

What do NATs do?

A

Transfer an acetyl group from acetyl-coenzyme A (Ac-CoA) to the a-amino group of the first amino acid residue of a protein.

49
Q

What is antagonistic acetylation?

A

Involved in gene expression regulation.
If a cell is exposing its genes to transcription factors or not depends on tightness of chromatin structure.
Acetylation removes the positive charge from histone which means DNA is wrapped less tightly.
This leads to an increase in transcription.

50
Q

Where does the methyl in methylation come from?

A

Methyl donated by S-adenosylmethionine.

51
Q

Is methylation reversible?

A

It is generally reversible and used to modulate a reaction.
Nitrogen methylation however are generally irreversible creating new amino acids.

52
Q

What is the function of arginine methylation?

A

This is the regulation of RNA processing
Gene transcription
DNA damage repair
Protein translocation
Signal transduction

53
Q

What is the function of lysine methylation?

A

Histone function regulation
Epigenetic regulation of transcription
Lysine Methyltransferase (KMT)

54
Q

What is p53?

A

Tumour suppressor activity.

55
Q

What is p53 activated by?

A

Various genotoxic stresses.

56
Q

What does p53 regulate?

A

Apoptosis
DNA repair
senescence
Autophagy