Figure 4.

rMAPKs of group A have basal kinase activity and are phosphorylated on a Tyr residue. rMAPKs stored in kinase storage buffer (rLeMPKs and rAtMPK6; see “Materials and Methods” for details) were run on SDS-PAGE gels and stained with Coomassie Brilliant Blue. Basal kinase activity was determined by incubation of the rMAPKs with MBP and radiolabeled ATP (middle panel) and a blot carrying the rMAPK proteins was incubated with antiserum specific for pY. rLeMPK3* represents an inactive form of the LeMPK3 enzyme obtained by storage in a solution without kinase storage buffer. [See online article for color version of this figure.]