抄録
Arabidopsis AtMEKK1 in full-length (AtMEKK1 full), kinase domain (AtMEKK1 kd) and several N-terminal deleted forms were isolated by RT-PCR. Out of these proteins, only 166-amino acid deleted (AtMEKK1 Δ166N) has kinase activity on MBP. The AtMEKK1 Δ166N phosphorylates special two Arabidopsis MAPKKs: AtMKK1 and AtMKK2. Phosphorylation activity is highest on AtMKK1. Yeast two hybrid method was employed to investigate the interaction. AtMEKK1 full and AtMEKK1 Δ166N show the interaction with AtMKK1, but not in the case of AtMEKK1 kd. These results indicate that 166 amino acid in the N-terminal region plays the role to block the phosphorylation and that another sequence of N-terminal region before the start amino acid of the kinase domain is important as substrate recognition. Additionally, the use of single, double and triple mutants of AtMKK1 gives an indication that T218 and S224 are the phosphorylation sites by AtMEKK1. Here, we show the AtMEKK1-MEK1-MPK4 signal cascade clearly.
