One). The X residue differs in Every class of MAPKs: ERK includes a threonine–glutamic acid–tyrosine (T–E–Y) motif, JNK includes a threonine–proline–tyrosine (T–P–Y) motif and p38 contains a threonine–glycine–tyrosine (T–G–Y) motif. Phosphorylation in the T–X–Y motif activates the MAPKs, allowing for phosphorylation of a selected repertoire of cytoplasmic and nuclear proteins https://emersonk653qzh3.magicianwiki.com/user