1. Reversible Binding of Phosphate
Unit 1 Cells and Proteins
Advanced Higher Biology
Miss Aitken

2. Post Translational Modification
Once proteins have been synthesised in the cell, a large portion of them undergo post-translational modification.
A number of proteins are inactive when first synthesised and require the addition of a phosphate molecule.

3. Adding or Removing Phosphate
The addition or removal of a phosphate causes reversible conformational (shape) changes in proteins.
It is an important method of regulating the activity of many proteins like enzymes or receptor molecules.

4. Adding or Removing Phosphate
Kinases catalyse phosphorylation (addition)
Approx 500 in the proteome
Phosphatases catalyse dephosphorylation (removal)
Approx 150 in the proteome
Important for signal transduction and control of the cell cycle

5. ATPases
ATPases are a group of transmembrane enzymes (enzymes which span the cell membrane) that use the phosphate from ATP to phosphorylate themselves, rather than a substrate.
Binding of phosphate changes their shape and alters their function. ATPases in the cell membrane are involved in the movement of ions across the cell membrane – for example, there are ATPases in the sodium-potassium pump.

6. Myosin and Actin
These proteins are involved in the movement of muscles and the movement of other parts of the cell.
The myosin protein has “heads” which reach out and bind to actin protein. Myosin then moves actin and this is how muscles contract.
There is a detailed guide on how this happens on page 27 of your Bright Red textbook.