Erk

Erk, is a MAP kinase which is activated by Mek (MAPKK) by phosphorylation. Erk uses ATP to phosphorylate different proteins involved in gene expression which activates transcription. This is part of a downstream signal, beginning with a signal molecule activating a receptor protein in the membrane. (Alberts et al, 2008, Molecular Biology of the cell, 5th edition, New York, Garland Science)