9: Post-translation And Regulation Flashcards

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1
Q

Briefly describe the general process in a cell between signalling ad the cell response?

A
  • A first messenger signalling molecule binds to a receptor on the cell membrane, or inside the cell.
  • Second messenger molecules relay the message through the cytoplasm. This is the process of transduction
  • An active effector (eg TF) allows a gene to be transcribed. This is the response
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2
Q

List some examples of post-translational modifications

A
  • Methylation, acetylation, myrisoylation
  • Ubiquitination
  • Glyosylation
  • Disulfide-bridge
  • Phosphorylation
  • Truncation
  • Protein-protein interactions
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3
Q

How does post translational modifications affect proteasome complexity?

A

P increases proteasome complexity
It increases the proteome to over a million different proteins

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4
Q

What is trimming

A

Truncation - removal of a part of the protein, mediated by protease

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5
Q

What are some examples of effects on proteins that PTMs can have post-synthesis?

A
  • Can affect the activity of protein
  • Folding of protein (interactions)
  • Degradation & stability
  • Translocation
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6
Q

What is phosphorylation?

A

The addition of a PO4 phosphate group to a protein/small molecule.
Occurs on serine, threonine, tyrosine

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7
Q

Is protein phosphorylation reversible?

A

Yes, phophatases can dephosphorylate substrate proteins

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8
Q

What is Ubiquitination?

A

Addition of one or several ubiquitin molecules to a target protein.
Results in the highly specific degradation of a protein

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9
Q

Which enzymes carry out ubiquitylation

A

E1, E2, and E3 enzymes

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10
Q

Which enzyme carries out the degradation of the ubiquitin proteasome system?

A

26S proteasome enzyme

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11
Q

Which enzymes carry out de-ubiquitylation?

A

DUBs - de-ubiquitylation enzymes

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12
Q

Briefly describe the process of ubiquitylation

A

1: Activation - Ub is activated by E1 enzyme in ATP-dependent reaction. Ub is conjugated to E1.
2: Conjugation - Activated Ub is transferred to E2, forming thioester bond
3: Ligation - E3 Ub ligase recognises & binds to target protein. E3 ligase facilitates transfer of Ub from E2 -> target protein.
4: Polyubiquitylation - Sometimes, multiple Ub are added to target protein. Occurs through attachment of Ub to a lysine residue. Different polyUb chains have different cellular consequences depending on what lysine residue it is added to.
5: Degradation/Regulation - Some Ub modifications result in the degradation of the attached target protein, others can affect protein localization, interactions, or activity.

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13
Q

What happens if a K48-linked poly ubiquitin chain is added?

A

Attached target protein is targeted for degradation by the proteasome

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14
Q

What is ubiquitin resistant to

A

Heat, pH extremes, and proteolysis

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15
Q

How many amino acids are in Ubiquitin?

A

76

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16
Q

What features of ubiquitin genes are conserved?

A
  • C terminal: RGG
  • Lysine residues at positions 6, 11, 27, 29, 33, 48, & 63