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Structural and Functional Studies on the Photosystem II Reaction centre

Ruffle, Stuart Vernon; (1993) Structural and Functional Studies on the Photosystem II Reaction centre. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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A three dimensional model of the Photosystem II (PS II) reaction centre has been generated by computer modelling based on the x-ray crystallographic derived structures of the reaction centres from two purple non-sulphur bacteria, following sequence alignment and secondary structure analysis. Analysis of the evolutionary relationship between the different Q-type reaction centre proteins has suggested that the ancestral complex was a homodimer. The model of the basic protein structure of PS II has allowed modelling experiments to be carried out to predict binding of bicarbonate, the water oxidizing complex and the herbicide DCMU. Several models of bicarbonate binding have been proposed to agree with the current biochemical and biophysical observations. Two orientations of DCMU in the QB binding site have been identified and a model has been proposed that links the two orientations with the DCMU effect on the QA-Fe2+ EPR signal. Computer generated structures have been modelled for the predicted transmembrane spans of the gene products psbE, F and I. PsbE and F gene products compose the cytochrome b559 complex, an integral part of PS II. Analysis of the sequence and secondary structure allows the construction of a variety of multimers some of which are presented. A method for isolating cytochrome b559 is presented and the effect of purification on the associated EPR signals is discussed. The effect of photoinhibition on PS II activity under aerobic, anaerobic and anoxic conditions has been studied in PS II samples prepared with the detergent heptyl thioglucopyranoside (HTG). The absence of oxygen predisposes the preparations to a loss of PS II activity under high light conditions. HTG preparations without bound bicarbonate are shown to be more sensitive to photodamage.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Structural and Functional Studies on the Photosystem II Reaction centre
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Biological sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10097739
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