Protein Synthesis II Flashcards Preview

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Flashcards in Protein Synthesis II Deck (23)
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1
Q

What is the function of chaperones?

A

Mediate proper folding of proteins

Hsp70 family are ATP-dependent

Bind and cover hydrophobic patches

2
Q

What is the function of protein disulfide isomerases?

A

Catalyzes the formation and cleavage of disulfide bonds

3
Q

What is the function of peptidyl prolyl isomerase?

A

Catalyze the transition of proline residues between the cis and trans configurations

4
Q

What are the three mechanisms of proteolytic processing?

A
  • Removal of the initiator methionine at the N-terminus
  • Cleavage of large precursors to form active enzymes or hormones
  • N-terminal signal sequence cleavage
5
Q

How is mature insulin formed?

A

Cleavage of a signal peptide and internal peptide

6
Q

What is co-translational translocation?

A

The active translation of proteins into the ER lumen via the rough ER.

7
Q

What is N-linked glycosylation?

A

Linkage of a carbohydrate to asparagine in the ER?

8
Q

What is O-linked glycosylation?

A

Linkage of a carbohydrate to a serine or threonine residue in the golgi apparatus

9
Q

What are calnexin and calreticulin?

A

Chaperone proteins that bind N-linked residue site when one glucose remains and stops binding when the last glucose is removed.

10
Q

What is the role of the folding sensor protein?

A

Determines if the protein is correctly folded or not.

Adds glucose back if not properly folded

11
Q

What is the role of glycosylphosphatidylinositol (GPI) anchors?

A

Attach proteins to the luminal side of the ER membrane.

Will eventually end up on the outside of the cell

12
Q

What is N-myristoylation?

A

Attachment of myristic acid to an N-terminal glycine residue.

Glycine is exposed by the removal of the initiating met residue

13
Q

What is palmitoylation?

A

Palmitic acid added to an internal cysteine residue

14
Q

What is the role of serine/threonine and tyrosine kinases?

A

Phosphorylation of specified residues on proteins

15
Q

What is the role of serine/threonine and tyrosine phosphatases?

A

Dephosphorylation of specifed residues on proteins

16
Q

What is nitrolysation?

A

Addition of NO groups to internal cysteine residues

Catalyzed by (de)Nitrosylases

17
Q

What is the unfolded protein response?

A

An excess of unfolded proteins leads to the expansion of the ER, production of more chaperones, and apoptosis in extreme cases.

18
Q

What is the function of IRE1?

A

Receptor that recognizes unfolded proteins and activates XP1 transcription factors

19
Q

What is the function of ATF6?

A

Receptor that recognizes ATF6, and cleaves, releasing ATF6 as a transcription factor

20
Q

What is the function of PERK?

A

Recognizes unfolded proteins and phosphorylates eIF2, blocking translation

Leads to the activation of ATF4 TF

21
Q

What is the function of XP1, ATF6, and ATF4?

A

TFs that target genes that encode chaperones, lipid synthesis enzymes, and ERAD proteins

22
Q

How are proteins degraded?

A

Ubiquitinated by Ubiquitin ligase.

Degree of ubiquitination determines the likelihood of degradation

23
Q

What are prion disorders?

A

infection with misfolded protein that stimulates other proteins to misfold.

Jakob-Crutzfeld, Kuru, Scrapie, Mad Cow