Photosystem II


What InterPro Tells Us


            The proteins that make up photosystem II are highly diverse in both sequence and structure.  Consequently, these proteins are placed in several different InterPro families, all of which are listed in the table of PSII proteins.  The description below is for the PSII reaction centre protein D1 (also known as PsbA or QB).


P02955 Spinach PSII reaction centre protein D1 (PsbA)


InterPro Domain Architecture


InterPro Entry

Method Accession

Graphical Match

Method Name

















            From the graphical match table above, you can see that the signatures (method accession) are divided into two InterPro entries for spinach PSII protein D1.  These entries give information about the family relationships of this protein.  IPR000484 represents the family of photosynthetic reaction centre proteins.  This is a large family that also contains PSII protein D2 (PsbD), as well as other homologous reaction centre proteins.  Four signatures represent this family:  PD000551 from the PRODOM database (based on C-terminus that connects to Mn cluster), PF00124 from the PFAM database (based on the conserved core), PR00256 from the PRINTS database (based on the transmembrane helical motifs), and PS00244 from the PROSITE database (based on residues around two conserved histidines that are ligands for the Mn and Fe atoms).  IPR005867 is a ‘child’ (subfamily) of IPR000484, representing more specifically the PSII protein D1 family (the PSII protein D2 family is represented by IPR005868, which is also a ‘child’ of IPR000484).  Only one signature represents this family, TIGR01151 from the TIGRFAM database.  To find out all the family relationships within IPR000484, you can either follow the individual links to the different ‘children’ in the IPR000484 entry page, or you can follow the link labelled ‘[tree]’ found directly underneath the ‘children’ tag (or follow the link provided here):



There are no separate domain entries for spinach PSII protein D1. 


What the Structure Tells Us


            There are structures available for photosystem II from different organisms in the Protein Data Bank (PDB).  A detailed description and visualisation of the structural features of photosystem II can be found at the PDB ‘Molecule of the Month’.  The crystallographic and X-ray structures of photosystem II provide insight into the mechanism of action of this photosynthetic reaction centre.


Next:  Table of Photosystem II Proteins

Previous:  The Proteins of Photosystem II