The EPR Spectrum of Tyrosine Z•and Its Decay Kinetics in O2-Evolving Photosystem II Preparations†

Biochemistry ◽  
2008 ◽  
Vol 47 (24) ◽  
pp. 6292-6300 ◽  
Author(s):  
Nikolaos Ioannidis ◽  
Georgia Zahariou ◽  
Vasili Petrouleas
Keyword(s):  
Photosystem Ii ◽  
Decay Kinetics ◽  
Epr Spectrum ◽  
Tyrosine Z

scholarly journals Evidence that D1 Processing Is Required for Manganese Binding and Extrinsic Protein Assembly into Photosystem II

2004 ◽  
Vol 279 (44) ◽  
pp. 45417-45422 ◽  
Author(s):  
Johnna L. Roose ◽  
Himadri B. Pakrasi
Keyword(s):  
Photosystem Ii ◽  
Mutant Cell ◽  
Protein A ◽  
D1 Protein ◽  
Fluorescence Decay ◽  
Normal Function ◽  
Temporal Position ◽  
Decay Kinetics ◽  
Fluorescence Decay Kinetics ◽  
Extrinsic Proteins

Photosystem II (PSII) is a large membrane protein complex that catalyzes oxidation of water to molecular oxygen. During its normal function, PSII is damaged and frequently turned over. The maturation of the D1 protein, a key component in PSII, is a critical step in PSII biogenesis. The precursor form of D1 (pD1) contains a C-terminal extension, which is removed by the protease CtpA to yield PSII complexes with oxygen evolution activity. To determine the temporal position of D1 processing in the PSII assembly pathway, PSII complexes containing only pD1 were isolated from a CtpA-deficient strain of the cyanobacteriumSynechocystis6803. Although membranes from the mutant cell had nearly 50% manganese, no manganese was detected in isolated ΔctpAHT3 PSII, indicating a severely decreased manganese affinity. However, chlorophyll fluorescence decay kinetics after a single saturating flash suggested that the donor YZwas accessible to exogenous Mn2+ions. Furthermore, the extrinsic proteins PsbO, PsbU, and PsbV were not present in PSII isolated from this mutant. However, PsbO and PsbV were present in mutant membranes, but the amount of PsbV protein was consistently less in the mutant membranes compared with the control membranes. We conclude that D1 processing precedes manganese binding and assembly of the extrinsic proteins into PSII. Interestingly, the Psb27 protein was found to be more abundant in ΔctpAHT3 PSII than in HT3 PSII, suggesting a possible role of Psb27 as an assembly factor during PSII biogenesis.

Complete EPR Spectrum of the S3-State of the Oxygen-Evolving Photosystem II

2009 ◽  
Vol 131 (14) ◽  
pp. 5050-5051 ◽  
Author(s):  
Alain Boussac ◽  
Miwa Sugiura ◽  
A. William Rutherford ◽  
Pierre Dorlet
Keyword(s):  
Photosystem Ii ◽  
Epr Spectrum ◽  
Oxygen Evolving

245 GHz High-Field EPR Study of Tyrosine-D° and Tyrosine-Z° in Mutants of Photosystem II†

Biochemistry ◽  
1996 ◽  
Vol 35 (3) ◽  
pp. 679-684 ◽  
Author(s):  
Sun Un ◽  
Xiao-Song Tang ◽  
Bruce A. Diner
Keyword(s):  
Photosystem Ii ◽  
High Field ◽  
Tyrosine Z ◽  
Tyrosine D

scholarly journals Water oxidation chemistry of photosystem II

2002 ◽  
Vol 357 (1426) ◽  
pp. 1395-1405 ◽  
Author(s):  
John S. Vrettos ◽  
Gary W. Brudvig
Keyword(s):  
Photosystem Ii ◽  
Water Oxidation ◽  
Ion Selectivity ◽  
Bound Water ◽  
Nucleophilic Attack ◽  
Manganese Cluster ◽  
Bond Forming ◽  
Proton Coupled Electron Transfer ◽  
Tyrosine Z ◽  
Oxidation Chemistry

The O 2 –evolving complex of photosystem II catalyses the light–driven four–electron oxidation of water to dioxygen in photosynthesis. In this article, the steps leading to photosynthetic O 2 evolution are discussed. Emphasis is given to the proton–coupled electron–transfer steps involved in oxidation of the manganese cluster by oxidized tyrosine Z (Y Z ), the function of Ca 2+ and the mechanism by which water is activated for formation of an O–O bond. Based on a consideration of the biophysical studies of photosystem II and inorganic manganese model chemistry, a mechanism for photosynthetic O 2 evolution is presented in which the O–O bond–forming step occurs via nucleophilic attack on an electron–deficient Mn V =O species by a calcium–bound water molecule. The proposed mechanism includes specific roles for the tetranuclear manganese cluster, calcium, chloride, Y Z and His190 of the D1 polypeptide. Recent studies of the ion selectivity of the calcium site in the O 2 –evolving complex and of a functional inorganic manganese model system that test key aspects of this mechanism are also discussed.

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