Lecture 15

Question 1

Post-translational modifications 6

Answer 1

1. Folding
2. Covalent alterations: phosphorylation, glycosylation, hydroxylation
3. Proteolytic processing: trimming
4. Protein degradation: ubiquitination
5. Addition of prosthetic groups: heme
6. Prenylation: lipid anchoring, farnesylation

Question 2

Phosphorylation location and protein

Answer 2

OH groups of serine and threonine, rarely tyrosine

By kinase

Question 3

2 types of glycosylation and protein

Answer 3

1. O-linked:
   To OH groups of ser and thr
   At Golgi
2. N-linked:
   To amide nitrogen of Asn
   ER and Golgi

Protein: glycotransferases

Question 4

Lipid anchoring examplle: Ras

Answer 4

Ras anchored to cytosolic side of PM through farnesyl group: a 15 C isoprenoid attached to cysteine

Question 5

Proteolytic processing of insulin

Answer 5

Preproinsulin: hydrophobic amino-terminal signal sequence targeting to ER cut
Proinsulin:remove internal peptide = C-peptide in Golgi
Insulin: A chain and B chain hold by disulfide bond