Co-operative research on plant intracellular proteases by biochemical and molecular biological methods

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Proteases of immature plants. The protease involved in processing of vacuolar proteins was purified, characterized and cloned, and the relationship between the processing and intracellular protein transport was clarified (Nishimura). A cysteine protease of germinating seed was purified, characterized and cloned (Minamikawa). A plant security system that prevents generation of free radical was clarified : plantsoverproduce apoproteins of chlorophyll-protein complexes relative to chlorophylls, and degrade excess apoprotein, preventing generation of free chlorophyll (Tanaka).Proteases of mature plants. The protease involved in the C-terminal processing of D1 protein was purified, characterized and cloned (Satoh). Photodegradation of cyanobacterial D1 protein was studied (Ikeuchi) and it was demonstrated that the degradation is caused by hydroxyl radicals that are necessarily generated by the functioning of photosystem II (Tokutomi). Proteases responsible for the degradation of extrinsic proteins of photosynthetic oxygen evolution complex were purified and characterized. One of them was found to be identical to polyphenol oxidase (Kuwabara). A stromal endopeptidase EP-1 was cloned (Kiyota). Susceptibility of FNR to an intrinsic protease was related to whether the N-terminal glutamine residue was pyroglutamylated in vivo (Shin). 26S-proteasome of plants was first purified and characterized (Nakagawa). Absence of calpain-related proteases in plants was suggested using anti-calpain IgG (Suzuki).Proteases of senescing plants A cysteine protease involved in cell death upon differentiation to tracheary elements was cloned (Fukuda). Cysteine proteases whose expression is induced by draft stress were cloned and the mechanism of the induction was studied (Shinozaki). Degradation of Rubisco during natural senescence was analyzed (Mae).