Spinach chloroplast ATP-dependent endopeptidase: Ti-like protease.

The soluble fraction of spinach chloroplast was used for purification and characterization of an ATP-dependent protease. Purification included Q Sepharose Fast Flow, hydroxylapatite and FPLC Superose 6 column chromatography. The isolated enzyme requires ATP and Mg2+ for stimulation and represents a ubiquitin independent serine protease, containing essential sulphydryl group(s). By using fluorogenic peptides a similarity of chloroplast protease to Escherichia coli Ti protease was observed. The chloroplast protease is immunochemically cross-reactive with the bacterial protease Ti.