Photosystem II. Molecular visualization for Photochemical & Photobiological Sciences journal cover

Photosytem II — one of the three major complexes of higher plants chloroplasts membranes and cyanobacteria tylacoid membrane.

With cytochrome b6f complex and photosystem I it forms photosynthetic apparatus, that provides conversion of light energy through several stages into organic compounds — products of photosynthesis.

First stage of this transformation occurs in photosystem II, as well as water oxidation and evolution of molecular oxygen.

Photosystem II — is a complex pigment-protein complex, that consist of: 20 different protein subunits, 35 molecules of chlorophill a (Chla), 11 molecules of β-carotine (Car), two pheophitines (Pheo), two plastoquinone molecules (PQ), two haems (Haem), bicarbonate molecule, 25 lipid molecules, four atoms of manganese, one chlorine atom and one atom of iron [1].

Working process of pigment-protein complex includes light-induced charge separation in the reaction center [2], electron transfer to secondary carrier QB [3], water oxidation with oxygen evolving complex to oxygen molecule and four ions of hydrogen [4] with following electron return to chlorophyll.

At the picture presented photosystem II complex in membrane without oxygen evolving complex.

Removal of oxygen evolving complex makes donor side accessible for outer red-ox active substances, and allows examination of such substances as electron donor for photosystem II.

In present case, synthetic complex, containing three atoms of manganese, serves as donor [5].