Post-Translational Modifications

Question 1

What is a Post-Translational Modification?

Answer 1

A modification to a protein before the protein can become functional

Question 2

What happens in a N- and C- terminal modification?

Answer 2

1 or 2 amino acids removed from N- and C- terminal ends

Question 3

What are some examples of Post-Translational Modifications?

Answer 3

1. N- or C- Terminal Modifications
2. Removal of Signal Sequences/Signal Peptides
3. Phosphorylation
4. Hydroxylation
5. Glycosylation

Question 4

What enzyme removes a signal sequence from a protein?

Answer 4

Signal Peptidase

Question 5

TRUE OR FALSE:

Cytosolic proteins have signal sequences

Answer 5

FALSE:

Only proteins being moved to organelles have signal sequences

Question 6

What is PROTEOLYTIC PROCESSING?

Answer 6

When protease cleaves a protein to modify its activity

Question 7

What is the precursor to insulin called?

Answer 7

Preproinsulin (110 amino acids)

Question 8

What is PHOSPHORYLATION?

Answer 8

The addition of a phosphate to a protein

Question 9

What THREE amino acids can the phosphate in phosphorylation be added to?

Answer 9

1. Serine
2. Threonine
3. Tyrosine

Question 10

What does PHOSPHORYLATION do?

Answer 10

It turns on/off the protein

increases or decreases the proteins activity

Question 11

What is HYDROXYLATION?

Answer 11

The addition of an OH group

Question 12

What is GLYCOSYLATION?

Answer 12

The addition of an oligosaccharide

Question 13

How can the oligosaccharide be aded during glycosylation?

Answer 13

N-linked to Asparagine

O-links to Serine or Threonine