Activation of the MAP kinase homologue RK requires the phosphorylation of Thr-180 and Tyr-182 and both residues are phosphorylated in chemically stressed KB cells.

A MAP kinase homologue, termed the reactivating kinase (RK), lies in a signalling pathway which mediates cellular responses to stress. Here we demonstrate that the stress-induced activation of the RK in human KB cells is accompanied by the phosphorylation of Thr-180 and Tyr-182, and that the phosphorylation of both residues is required for the activation of this enzyme.