Impact of dimeric organization of enzyme on its function: the case of photosynthetic water splitting.
BACKGROUND
It is a question of whether the supramolecular organization of the protein complex has an impact on its function, or not. In the case of the photosystem II (PSII), water splitting might be influenced by cooperation of the PSIIs. Since PSII is the source of the atmospheric oxygen and because better understanding of the water splitting may contribute to the effective use of water as an alternative energy source, possible cooperation should be analyzed and discussed.


RESULTS
We suggest that the dimeric organization of the PSII induces cooperation in the water splitting. We show that the model of monomeric PSII is unable to produce the oxygen after the second short flash (associated with the double turnover of the PSII), in contrast to the experimental data and model of dimeric PSII with considered cooperation. On the basis of this fact and partially from the support from other studies, we concluded that the double turnover of the PSII induced by short flashes might be caused by the cooperation in the water splitting. We further discuss a possibility that the known pathway of the electron transport through the PSII might be incomplete and besides D1-Y161, other cofactor which is able to oxidize the special chlorophyll pair (P680) must be considered in the monomeric PSII to explain the oxygen production after the second short flash.


BACKGROUND
Commented SBML codes (.XML files) of the monomeric and dimeric PSII models will be available (at the time of publication) in the BioModels database (www.ebi.ac.uk/biomodels).
Jablonsky
Jiri
J
Laboratory of Biophysics, Faculty of Science, Palacky University, Tr. Svobody 26, 771 46 Olomouc, Czech Republic.
Susila
Petr
P
Lazar
Dusan
D
D003198:Computer Simulation; D019281:Dimerization; D008958:Models, Molecular; D010100:Oxygen / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism*; D014867:Water / Q000737:chemistry / Q000378:metabolism*
D045332:Photosystem II Protein Complex; D014867:Water; D010100:Oxygen