Question

How does a phosphorylation cascade work? What does it do to the original signal?

Answer 1

A series of phosphorylations can lead to enhancement of the original signal.

Explanation:

Phosphorylation of proteins can alter the activity of that protein, either inhibitory or stimulatory. Ìn signaling cascades it is most often stimulatory. Kinases are enzymes responsible for this phosphorylation.

Phosphorylation reactions often occur in series, or cascades, in which one kinase activates the next. These cascades serve to amplify the original signal, but also improving the signal (less noise) and allowing for cross talk between different pathways.

A well known example is the MAP kinase cascade:

Ras activates the Raf kinase, which activates the MEK kinase, which in turn activates the ERK kinase.

To turn of the signal, the proteins will be dephosphorylated.