Figure 1

Structure-based sequence alignment of Arabidopsis MPK6 with several non-plant MAPKs and kinase activity assays of the different truncated MPK6 proteins.

(A) Multiple sequence alignment of Arabidopsis MPK6 (PDB code: 5CI6), rat ERK2 (PDB code: 1ERK), mouse p38 (PDB code: 1P38) and human JNK1 (PDB code: 1UKH). MPK6 shares 50% sequence identity with ERK2, 45% with p38 and 36%with JNK1. The roman numerals indicate the subdomains of the MAPKs. The residues written in lowercase and italicized letters indicate the residues that were not included in the structure but were used for the crystallographic studies. The secondary structure elements of MPK6 are indicated above the sequences, with open boxes representing the α and 3/10 helices and open arrows representing the β strands. The dashed lines denote the secondary structures that were presented in ERK2 but not MPK6. The glycine-rich loop, phosphorylation lip and MAPK insert are also labelled. (B) In vitro phosphorylation of the recombinant MPK6 protein and its truncated mutant proteins by the active MKK5 (MKK5^DD). (C) Kinase activity of the recombinant MPK6 protein and its truncated mutants after phosphorylation by the active MKK5 (MKK5^DD). Myelin basic protein was used as the substrate.