The 1-aminocyclopropane-1-carboxylate (ACC) oxidase catalyzes the last step in the biosynthesis of ethylene from ACC in higher plants. The complex structure of ACC oxidase/Fe2+/H2O derived from Petunia hybrida has recently been established by X-ray crystallography and it provides a vast structural information for ACC oxidase. Our mutagenesis study shows that both Lys296 and Arg299 residues in the C-terminal helix play important roles in enzyme activity. Both K296R and R299K mutant proteins retain only 30-15% of their enzyme activities with respect to that of the wild-type, implying that the positive charges of C-terminal residues are involved in enzymatic reaction. Furthermore, the sequence alignment of ACC oxidases from 24 different species indicates an existence of the exclusively conserved motif (Lys296-Glu301) especially in the C-terminus. The structure model based on our findings suggests that the positive-charged surface in the C-terminal helix of the ACC oxidase could be a major stabilizer in the spatial arrangement of reactants and that the positive-charge network between the active site and C-terminus is critical for ACC oxidase activity.
Bibliographical noteFunding Information:
This study was supported by the Ministry of Science and Technology of Korea/The Korea Science and Engineering Foundation through the NRL program of MOST NRDP (M1-0203-00-0020) and by Protein Network Research Center (W.L.). This work was also supported by grants from Rural Development Administration (BioGreen 21 Program), Plant Diversity Research Center (21st Century Frontier Research Program of MOST Project No. PF 0330404-00), KOSEF (Plant Metabolism Research Center, Kyung Hee University) (W.T.K.) and in part by Brain Korea Project 21 (BK21) (W.L., W.T.K. and D.R.Y.).
All Science Journal Classification (ASJC) codes
- Structural Biology