Particles of photosystem 2 contain plantacyanin.

PS2 particles prepared from chloroplasts of three plant species were shown to contain the basic blue copper protein, plantacyanin, which may be extracted from the particles by concentrated saline solutions containing Triton X-100. Antibodies to plantacyanin were found to inhibit the photosynthetic oxygen evolution performed by the particles. Thus, evidences were obtained for participation of this protein in the oxygen-evolving activity of PS2 particles.