Reversible Binding of Phosphate

Question 1

What is phosphorylation and what does is it used for?

Answer 1

• Phosphorylation is where a phosphate is added and is a common form of post-translational modification.
• Phosphorylation regulates protein activity by causing reversible conformational changes and it is critical for signal transduction.
• Adding/removing a phosphate can activate or inactivate a protein depending on how the proteins conformation is changed.

Question 2

What are kinases and phosphatases and what do they do?

Answer 2

They are enzymes. Kinases phosphorylate proteins (their substrate) using phosphate from ATP and phosphotases dephosphorylate proteins (their substrate).

Question 3

What are ATPases and what do they do?

Answer 3

ATPases are a group of transmembrane enzymes that use phosphate from ATP to phophorylate themselves. The phosphate binding changes their conformation and so changes their function. They are involved in active transport of ions across the membrane and the sodium-potassium pump.

Question 4

What is myosin and actin?

Answer 4

Myosin and actin are proteins involved in muscle contraction and movements in cells such as cytokineses. The myosin has ‘heads’ that reach out to form cross-bridges with actin. Myosin moves actin along.

Question 5

How does myosin and actin work?

Answer 5

1) Myosin heads are bound to actin.
2) ATP binds to myosin which causes a conformation change - myosin detaches from actin and swings forwards.
3) ATP is broked down ADP and phosphate which causes another confromation change - the myosin head rebinds to actin.
4) The rebinding to actin causes another conformational change - ADP and phosphate are released.
5) The myosin adopts its original confromation, dragging the actin filament with it.