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A cysteine protease from maize isolated in a complex with cystatin
T Yamada1, H Ohta, A Shinohara
1Department of Biological Sciences, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Japan. tyamada@bio.titech.ac.jp
Plant & Cell Physiology
|May 5, 2000
Summary
Researchers identified a novel plant protease complex from maize, comprising a cysteine protease and a cystatin inhibitor. This finding reveals a new mechanism for protease regulation in plants.
Area of Science:
- Plant Biochemistry
- Proteomics
- Molecular Biology
Background:
- A latent protease complex was previously purified from maize.
- The complex's composition and activation mechanism were not fully understood.
Purpose of the Study:
- To elucidate the composition and function of the maize protease complex.
- To characterize the isolated cysteine protease and its inhibitor.
Main Methods:
- Protein purification and complex isolation.
- Cloning and expression of the cysteine protease in Escherichia coli.
- Analysis of substrate and inhibitor specificities.
Main Results:
- The maize protease complex consists of a 40 kDa cysteine protease and a 15/13 kDa cystatin.
- The cloned cysteine protease exhibits high homology to other plant cysteine proteases.
- Recombinant protease expressed in E. coli showed similar specificities but lacked latency, suggesting cystatin's role.
Conclusions:
- This is the first report of a plant cystatin-cysteine protease complex.
- Cystatin binding likely causes the protease's latent state, with SDS activating it by dissociation.
- Protease mRNA is widely distributed in maize tissues, excluding seeds.