Post Transational Modifications Flashcards Preview

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Flashcards in Post Transational Modifications Deck (24):
1

What is post-translational modification?

Additional processing after a protein is made

2

What is proteolytic cleavage?

Breaking peptide binds to remove part of the protein

3

What is chemical modification?

Addition of functional groups to amino acid residues

4

What kind of proteins are synthesised on free ribosomes?

Proteins for cytosol or posttranlational import into organelles

5

What kind of proteins are synthesised by ribosomes on the RER?

Proteins for membrane or secretory pathway

6

What is required for protein sorting?

Signal
Receptor
Translocation machinery
Energy

7

What must proteins targeting peroxisomes have?

Must have the peroxisomes targeting sequence -Serine, lysine, leucine at c terminus usually
This is recognised by the pex5 which binds to cargo protein
This binds to the 13 per protein channel across peroxisomal membrane
ATP hydrolysis recycles PTS receptor

8

What disorders are caused if peroxisomes targeting goes wrong?

Peroxisomes biogenesis disorders
Zellweger syndrome
Rhizomelic chondroysplasia punctata

9

What is constitutive secretion?

All the time/continuous secretion

10

What do endocrine cells secrete?

Hormones

11

What do exocrine cells secrete?

Digestive juices

12

What do neurocrine cells secrete?

Neurotransmitters

13

What is a signal sequence?

At the n terminus
5-30 amino acids in length
Form alpha helix
Central region hydrophobic

14

What is the signal recognition particle?

Receptor needed to bind the signal peptide on proteins destined for the ER
6 proteins and a short piece of RNA
Recognises signal peptide and ribosome

15

What are the functions of the endoplasmic reticulum?

Insert proteins into membranes
Specific proteolytic cleavage
Glycosylation
Forms S-S bonds
Folds proteins
Assembles multisubunit proteins
Hydroxylation of selected lys and pro residues

16

What is glycosylation?

Addition of sugars

17

Why is glycosylation of proteins important?

Correct protein folding
Protein stability
Facilitates interactions with other molecules
Deficiencies in n linked glycosylation leads to CDG

18

What protein helps from disulphide bonds?

Disulphide isomerise

19

What happens if there are folding problems with a protein?

May be trapped in misfolded conformation
Mutation
Incorrectly associate with another sub unit

20

What do ER chaperones do?

Retain unfolded proteins in ER
Act as sensor to monitor extent of protein mis folding

21

What happens if misfolding of proteins cannot be corrected?

Degradationin cytosol
Accumulate to toxic levels and cause disease

22

Where does o linked glycosylation occur and what happens?

In Golgi
Sugar attach to hydroxyl group of serine and threonine

23

What is proteolytic cleavage?

Breaking of a peptide bond to remove part of the protein

24

What is chemical modification?

Addition of functional groups to amino acid residues