B. Apoproteins of Photosystem II (PSI)
Photosystem II is a multiprotein supracomplex embedded in the thylakoid membrane. It consists of both membrane-spanning (intrinsic) proteins and surface bound (extrinsic proteins) (for a review see Akerlund, 1993). In higher plants it consists of about 20 different proteins and 7 different prosthetic groups. It has an estimated molecular mass of 1.0-1.5 MDa. Twenty to thirty percent of the molecular mass consists of chlorophyll.
The proteins of PSII can be classified into 6 different categories:
- . Reaction center apoproteins
- . Inner Chl a antennae
- . The major outer antenna system (LHCII)
- . Minor outer antennae
- . Extrinsic proteins, and
- . Other miscellaneous protein components
The reaction center apoproteins and the inner Chl a antennae constitute the central core of PSII. The central core complex represents the minimal structure capable of oxygen evolution under expermental conditions.
References
- Akelund, H-E (1993). Function and organization of photosystem II. In: Pigment-Protein Complexes In Plastids: Synthesis and Assembly . C. Sundqvist and M. Ryberg, (eds.), p 419-445, Academic Press, New York.