eLA Post Translational Modification of Proteins

Question 1

3 most commonly phosphorylated AA’s

Answer 1

Serine, Threonine, and Tyrosine

Question 2

consensus sequence

Answer 2

the AA sequences around the target residue needing to be phosphorylated

Question 3

Three families of phosphatases

Answer 3

1. Serine/Threonine phosphatases: remove Pi from Ser and Thr
2. Tyrosine phosphatases: remove Pi from Tyr
3. Phosphoprotein phosphatases: remove Pi from Ser, Thr, and Tyr

Question 4

enzyme and substrate used for protein methylation

Answer 4

Protein methyltransferase and SAM (S-adenosylmethionine)

Question 5

SET domain

Answer 5

conserved 130AA domain of protein methyltransferases that forms a B-sheet catalytic core

Question 6

O-methylation

Answer 6

• occurs on the carboxylate side chains of Asp and Glu
• reversible
• results in loss of negative charge

Question 7

N-methylation

Answer 7

• occurs on Lys, His, Arg, Gln, and Asn
• reversible
• results in increased hydrophobicity

Question 8

N-terminal acetylation

Answer 8

• very common in eukaryotes, rare in prokaryotes

- irreversible

Question 9

Histone acetylation

Answer 9

• occurs on Lys residues of histone tails
• reversible
• done by HATs
• reversed by HDACs

Question 10

Myristoylation

Answer 10

• occurs in eukaryotes, but not prokaryotes
• adding a C14 lipid group to a protein
• done by NMTs
• has a sequence indicator

Question 11

Palmitoylation

Answer 11

• reversible (on or off function)
• adding a C16 lipid group to a protein
• done by PATs
• has no sequence indicator

Question 12

Prenylation

Answer 12

• adding a C15 lipid group to the Cys residue of proteins
• 2% of eukaryotic proteins are prenylated, very rare in prokaryotes
• has a consensus sequence

Question 13

How is p53 activated?

Answer 13

To activate p53, it is phosphorylated. Phosphorylation serves as a signal to suppress p53 degradation. Many cancers have mutated p53 genes.