Studies on plantacyanin. I. Distribution in the plant kingdom, subcellular localization and physicochemical properties.

The standard preparative procedure used earlier for the isolation of plantacyanin from cucumber peelings and spinach leaves was employed for the detection of this protein in 15 plants. It was found that four of these 15 species of plants contain plantacyanin. From the study of the subcellular distribution of plantacyanin in spinach leaves, it has been concluded that the protein is associated with chloroplasts. Macromolecular properties as well as optical, fluorescence and EPR spectra of plantacyanin from cucumber were studied. It has been shown that at alkaline pH, a short living state of the protein active site is formed. This state (state 3) has an absorption band at 575 nm. The incubation of the protein in alkaline media under anaerobic conditions brings about the bleaching of plantacyanin accompanied by the disappearance of the EPR signal. The effect of some protein-modifying agents was studied and the data obtained are discussed from the point of view of possible ligand amino acids of copper in plantacyanin. The protein copper can be removed by diethyldithiocarbamate and the procedure of reconstitution of holoprotein from apoprotein and Cu2+ was developed.