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BMS2002: Cell Bio and Disease > L2: Post Translational Modification > Flashcards

L2: Post Translational Modification Flashcards

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1
Q

What happens in post translational modification (PTM)?

A

AA sequences is altered in terms of adding or removing aspects of the peptide, to change the way it folds
- thereby changing the final tertiary + quatermary structuring giving it different functions

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2
Q

When does PTM occur?

A

After protein biosyntheis on the aa chain or at a terminal

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3
Q

What are pluripotent stem cells?

A

Cells that can potentially differentiate into any cell in the human body

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4
Q

How does PTM affect the proteome?

A

It increase proteome diversity whilst extending functino and stability

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5
Q

Name the 5 common types of PTM

A
  • phosphorylation
  • methylation
  • acetylation
  • glycosylation
  • disulfide bonds
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6
Q

What are the 4 methods of introducing new functional groups?

A
  • phosphorylation
  • glycolysation
  • acetylation
  • methylation
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7
Q

Explain how phosphorylation can be used to add new functional groups

A

Phosphate can be added or removed causing conformational change in protein, which can activate or deactivate an enzyme

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8
Q

What is phosphorylation

A

The adding of phosphate groups to the protein, therefore changing the electric nature of the aa

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9
Q

How does phosphorylation change the nature of an AA?

A
  • changes bonding patterns, angles between adjacent AAs and interactions with other AAs
  • thus changes the shape and structure and potentially its enzymatic processes
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10
Q

What are the possible outcomes of phopshorylation

A
  • significant conformational change from the 2 -ve charges from the phosphate
  • form a site recognised by other proteins
  • can mask a binding site preventing protein- protein interaction
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11
Q

How can the transfer or removal of a phosphate group be catalysed?

A
  • Protein kinases catalyse transfer using ATP

- Phosphates catalyse removal by hydrolysis. Can be specific or non, controlled by regulatory proteins

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12
Q

What is glcosylation?

A

When a carbohydrate is covalently bound to a functonal group, occuring in both euk and prokary cells

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13
Q

What are the functions of glycosylation?

A
  • helps correct folding
  • increases protein stability (particularly significant in secreted proteins)
  • cell to cell/ cell to environment adhesion
  • immune response
  • hormone activity
  • embryonic development
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14
Q

What is the purpose of dolichol?

A

Used to anchor carbohydrates and is where they are built on

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15
Q

Explain the 5 types of glycosylation

A
  1. N-linked: glycan binds to aa of Asp in ER (e.g. insulin receptor)
  2. O-linked: monosaccs bind to OH group serine or threonine in ER, golgi, cytosol & nucleus (e.g. collagen)
  3. Glypiatan: glycan core links phospholipid & protein (e.g. anchors cell surface proteins)
  4. C-linked: mannose binds to the indole ring of trytophan (e.g. only in mammalian cells, ECM)
  5. Phosphoglycosylation: glycan binds to serine via phosphodiester bond
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16
Q

What is acetylation?

A

The addition/ removal of an acetyl group donated by acetyl co-enzyme A
- can be enzymatic or non using acetylase & deacetylase

17
Q

When can acetylation occur?

A

Co or post translational modification

18
Q

Name the 3 main types of acetylation

A
  • N terminal acetlation
  • Lysine acetylation
  • Anatagonistic acetylation/ deacetylation
19
Q

Which type of acetylation is the most common in eukaryotes?

A

N terminal being used in synthesis, localiation and stability

20
Q

How is N-terminal acetylation catalysed?

A

Using N-terminal acetyltransferases (NATs) which transfer an acetyl group to the alpha-amino group of 1st AA residue of protein
- different NATs are responsible for acetylation of nascent protein N termini

21
Q

Briefly explain lysine acetylation

A

The transfer of an acetyl group to the primary amine in the ε-position of the lysine side chain within a protein

  • involved in activation of gene expression
  • often linked to tcn factors (e.g. p53)
22
Q

Explain the process of antagonistic acetylation/ deacetylation

A

This method regulates gene expression, occuring in cytoplasm or nucleus (e.g. histones)

  • acetylation removes +ve charge from histones so DNA wraps less tightly
  • involved in synthesis, stability and localisation of other proteins
23
Q

How does acetylation affect histones?

A

Acetylation of histones encourages binding of effector proteins, relaxation of chromatin conformation and increase in txn

24
Q

High levels of acetylation are associated with what?

A

Transcriptional hyperactivity

25
Q

List therapeutic application of antagonistic acetylation

A
  • targetting HDACs in malignant cells
  • treatment of neurodegenerative disease
  • development of small molecule inhibitors (HDI)
  • Best known: suberoylniline hydroxamic acids in breaking cutaneous T cell lymphoma
26
Q

What is methylation?

A

The transfer of a methyl group, mainly onto a
- lysine (once, twice or thrice)
or
- arginine (once or twice)

27
Q

Lysine methylation is irreversible. True or false?

A

False, it can be reversed reverting activation or supression action

28
Q

Carbonyl and nitrogen methylation are both irreversible. True or false?

A

False. Nitrogen methylation is irreversible creating new AAs, but carbonyl methylation is reversible and can be used to modulate a reaction

29
Q

What is arginine methylation involved in?

A
  • regulation of RNA processing
  • gene transcription
  • DDR
  • protein translocation
  • signal transduction
30
Q

What effect does arginine methylation have?

A

Effects protein- protein interaction in process, mostly affecting RNA binding proteins and also effecting protein traffickingm signal transduction and txn regulation
- linked to histone acetylatino

31
Q

What is the role of lysine methylation and give an example?

A

Regulates histone function and the epigenetics of txn using lysine methyltransferase (KMT) e.g. p53

  • p53 is rich in Lys and Arg
  • its activity is regulated by comlex array of PMT acetylation, phosphorylatoin & methylatoin
  • acetylation stabilises p53 increasing DNA interaction

BMS2002: Cell Bio and Disease (16 decks)

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