Phototsystem II is the first protein in the light harvesting reactions in the photosynthetic process in plants, algae, and cyanobacteria. Its role: to split water into elemental oxygen and
Molecule of hte month

A cartoon rendering of Photosystem II as seen on the RCSB's molecule of the month blog.

harvest electrons and protons from water, using just light energy. The key characteristic of this protein is its complex interactions with ligands of Chlorophyll a, Plastoquinone, Pheophytin, and β-Carotene. Photosystem II is considered one of the most important proteins to ever evolve, as it is the source of nearly all oxygen in our atmosphere. It maintains the ozone layer that protects us from the sun's harmful UV radiation and supplies the reduced equivalents to fix carbon into organic molecules.

PS II consists of two main proteins: the Light-Harvesting Complex (LHC) and the Oxygen Evolving center (OEC). These two proteins work in tandem to split water into elemental oxygen, protons, and electrons.

Protein Data and InformationEdit


  1. Rogelio: Photosystem II: Introduction
  2. Rogelio: Photosystem II: Biological function
  3. Rogelio: Photosystem II: Biosynthesis
  4. Rogelio: Photosystem II: Gene sequence
  5. Rogelio: Photosystem II: Amino acid sequence and composition
  6. Rogelio: Photosystem II: Secondary and tertiary structure
  7. Rogelio: Photosystem II: Domains and structural motifs
  8. Rogelio: Photosystem II: Interactions with macromolecules and small molecules
  9. Rogelio: Photosystem II: Molecular biodiversity and evolution
  10. Rogelio: Photosystem II: Literature overview
  11. Rogelio: Photosystem II: Useful online resources