Photosystem II (Thermosynechococcus elongatus)1,2

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This dimer from T. elongatus is responsible for absorbing light energy, oxidizing H2O to O2, and sending the excited electrons through an electron transport chain.  Through this ETC, plants produce the energy required to produce glucose.  

Protein Cartoon

Notice the pink region: it contains several transmembrane helices spanning the thylakoid membrane.  The gold region and part of the pink are located in the lumen of the thylakoid. 

Photosystem II 12 kDa extrinsic protein (PsbU)

PsbU is an extrinsic protein of the photosystem II complex. PsbU stabilizes the oxygen-evolving machinery of the photosystem II complex against heat-induced inactivation.

Core Light Harvesting Protein (cyan) and CP43 (yellow)

These proteins bind the chlorophyll, which absorb light.

 

α Chlorophyll a

Responsible for absorbing light in the visible region and exciting electrons derived from H2O.   

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Oxygen Evolving Centers (OEC)

At these sites, water is oxidized to H2O, "one of the most thermodynamically demanding reactions in biology1." The oxygen evolving center locations are located at the yellow points. 

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Detailed OEC (Mn cluster)

The PSII dimer contains two OECs: OEC-1 and OEC-2001.  Mn3CaO4--Mn (linked via mono-µ-oxo bridge)

by Brian Hansen and Cathy Weber

 

1Ferreira, K.N.,  Iverson, T.M.,  Maghlaoui, K.,  Barber, J.,  Iwata, S. "Architecture of the Photosynthetic Oxygen-Evolving Center" Science v303 pp.1831-1838 , 2004

2RCSB Protein Data Bank

http://www.rcsb.org/pdb/