ISSN:
1573-5079
Keywords:
electron paramagnetic resonance
;
managanese cluster
;
oxygen evolution
;
oxygen evolving complex
;
Photosystem II
;
proton transfer
;
tyrosine radical
;
water oxidation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Recent magnetic-resonance work on YŻ suggests that this species exhibits considerable motional flexibility in its functional site and that its phenol oxygen is not involved in a well-ordered hydrogen-bond interaction (Tang et al., submitted; Tommos et al., in press). Both of these observations are inconsistent with a simple electron-transfer function for this radical in photosynthetic water oxidation. By considering the roles of catalytically active amino acid radicals in other enzymes and recent data on the water-oxidation process in Photosystem II, we rationalize these observations by suggesting that YŻ functions to abstract hydrogen atoms from aquo- and hydroxy-bound managanese ions in the (Mn)4 cluster on each S-state transition. The hydrogen-atom abstraction process may occur either by sequential or concerted kinetic pathways. Within this model, the (Mn)4/YZ center forms a single catalytic center that comprises the Oxygen Evolving Complex in Photosystem II.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00020428
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