Photosystem II contains 20 different protein subunits all in the light capturing family, There are two main subunits, D1 and D2. Theses subunits are completely symmetrical and are joined by covalent bonds. Both of these subunits contain the reaction center chlorophyll molecules (P680) along with the other molecules used for electron and proton shuttling. The Oxygen Evolving Complex is at the heart of the photosystem two proteins and is held in place by eleven different side chains.

Membrane DomainsEdit

Of the 20 subunits in both the D1 and D2 dimers, 18 of them posses highly alpha-helical structures. This structure is consistent with PS II location in the thylakoid membrane stacks in plants and cyanobacteria

Membranew ith lables

This image of a surface representation of the D1 subunit (right) and a cartoon of the D2 subunit (left). The bracketed region in yellow indicates that thickness of the trans-membrane domain that sits in the thylakoid membrane with value of 36.5 Angstroms. The bracketed region is the length of the protein through its longest axis 195.0 Angstroms.

OEC RAY label

Ball-and-stick representation of the OEC. The spheres in red are oxygen, spheres in pink are Manganese, the sphere in grey in calcium.


  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