Erk

Erk, is a MAP kinase which is activated by Mek (MAPKK) by phosphorylation and is involved in the Ras signalling pathway. Erk uses ATP to phosphorylate different proteins involved in gene expression which activates transcription. This is part of a downstream signal - a phosphorylation cascade - beginning with a signal molecule activating a receptor protein in the membrane ^[1]. Other than Erk and Mek there is a third MAP kinase called Raf that activates Mek. Once each MAP kinase is used it is deactivated by phosphatase (removes phosphate).

References

1. ↑ Alberts et al, 2008, Molecular Biology of the cell, 5th edition, New York, Garland Science