Influence of the axial ligand on the cationic properties of the chlorophyll pair in photosystem II from Thermosynechococcus vulcanus.
Influence of the axial ligand of PD1 chlorophyll (D1-His-198) on the Em of monomer chlorophylls PD1 and PD2, and the PD1•+/PD2•+ charge ratio was investigated by theoretical calculations using the PSII crystal structure of Thermosynechococcus vulcanus analyzed at 1.9-Å resolution. It was found that the Em(PD1)/Em(PD2) values and PD1•+/PD2•+ ratio remained unchanged upon D1-H198Q mutation. However, Em(PD1) was increased in the D1-H198A mutant, resulting in a more even distribution of the positive charge over PD1/PD2. Introduction of a water molecule as an axial ligand resulted in equal Em values and PD1•+/PD2•+ ratios between the mutant and wild-type, thus confirming the presence of the water ligand in the mutant.
Career-Path Promotion Unit for Young Life Scientists, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
Keisuke
K
Saito
Jian-Ren
JR
Shen
Hiroshi
H
Ishikita
D002412:Cations; D002734:Chlorophyll / Q000737:chemistry*; D000458:Cyanobacteria / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry; D045332:Photosystem II Protein Complex / Q000737:chemistry*; D011789:Quantum Theory; D046939:Synechocystis / Q000378:metabolism; D013816:Thermodynamics
D002412:Cations; D008024:Ligands; D050505:Mutant Proteins; D045332:Photosystem II Protein Complex; D002734:Chlorophyll