Lecture 7: Post-translational modificaitons

Question 1

What are the two categories of protein PTM?

Answer 1

1. Covalent addition of a chemical group to an animo acid side chain
2. Covalent hydrolysis of a peptide bond in a protein

Question 2

What are post-translational modifications?

Answer 2

Are modifications that are added to a portion giving it specific properties and increasing functional diversity of the proteome
- PTM’s are attached after transcription and translation and occur primarily in the Golgi while the protein passes through the endomembrane system

Question 3

What is phosphorylation catalysed by?

What is dephosphorylation catalysed by?

Answer 3

• Kinase enzymes

- Phosphatase enzymes

Question 4

What side chains does phosphorylation occur on?

Answer 4

• Serine
• Threonine
• Tyrosine

Question 5

What is phosphorylation ?

What is its effect?

What are 2 examples?

Answer 5

The addition of a charged phosphate group to a hydroxyl group.

• induces a localises conformation change affects the function
  e. g insulin receptor & Na+/K+ pump

Question 6

What is gamma-carboxy glutamic acid?

What is its effect?

Answer 6

Occurs when an a carboxyl groups covalently linked to glutamic acid forming Gla.

Gla enables formation of bidentate Ca2+ binding sites which enables blood coagulation proteins to interact with platelets as part of the blood clotting process
- requires Vitamin K as a cofactor

Question 7

What is hydroxylation? Where does it occur?

What is its effect?

What is required?

Answer 7

Occurs on the 4’position of Pro or 5’ position of Lys. Collagen is hydroxylated

• increases non-covalent interaction possibilities - more hydroxylation the stronger the higher order collagen structure
• Vitamin C is required