Plastocianinon

Plastocianinon is not a widely recognized term in biological nomenclature. It may be a misspelling or a fictional name. If you meant plastocyanin, the following summarizes its properties.

Plastocyanin is a small copper-containing protein that functions as a mobile electron carrier in photosynthesis. It transfers electrons between the cytochrome b6f complex and photosystem I in the thylakoid lumen of chloroplasts in green plants and algae, and in cyanobacteria.

Plastocyanin is about 100 to 110 amino acids long and contains a single copper ion coordinated by a type 1 blue copper center, with ligands typically provided by two histidines, a cysteine, and a weak axial ligand such as a methionine. This arrangement gives it a characteristic blue color and enables rapid electron transfer.

Its copper center cycles between Cu(I) and Cu(II) states, with redox potentials typically around +0.37 to +0.46 V versus the normal hydrogen electrode, depending on species and conditions.

Plastocyanin accepts electrons from cytochrome f and donates them to photosystem I (P700+), thereby serving as a crucial intermediary in the light reactions of photosynthesis. The protein is soluble and located in the thylakoid lumen.

Plastocyanin is highly conserved across oxygenic photoautotrophs, reflecting its essential role in photosynthetic electron transport.

First characterized in the 1960s in spinach, plastocyanin has since been a model system for studying blue copper proteins and electron transfer mechanisms.