Analysis of the proposed Fe-SX binding region of Photosystem 1 by site directed mutation of PsaA in Chlamydomonas reinhardtii

Hallahan, B. J., Purton, S., Ivison, A., Wright, D. and Evans, M. C. W. (1995) Analysis of the proposed Fe-SX binding region of Photosystem 1 by site directed mutation of PsaA in Chlamydomonas reinhardtii. Photosynthesis Research, 46(1-2), pp. 257-264. (doi:10.1007/BF00020438) (PMID:24301590)

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Abstract

The psaA and psaB genes of the chloroplast genome in oxygenic photosynthetic organisms code for the major peptides of the Photosystem 1 reaction center. A heterodimer of the two polypeptides PsaA and PsaB is thought to bind the reaction center chlorophyll, P700, and the early electron acceptors A0, A1 and Fe-SX. Fe-SX is a 4Fe4S center requiring 4 cysteine residues as ligands from the protein. As PsaA and PsaB have only three and two conserved cysteine residues respectively, it has been proposed by several groups that Fe-SX is an unusual inter-peptide center liganded by two cysteines from each peptide. This hypothesis has been tested by site directed mutagenesis of PsaA residue C575 and the adjacent D576. The C575D mutant does not assemble Photosystem 1. The C575H mutant contains a photoxidisable chlorophyll with EPR properties of P700, but no other Photosystem 1 function has been detected. The D576L mutant assembles a modified Photosystem 1 in which the EPR properties of the Fe-SA/B centers are altered. The results confirm the importance of the conserved cysteine motif region in Photosystem 1 structure.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Wright, Mr Derek
Authors: Hallahan, B. J., Purton, S., Ivison, A., Wright, D., and Evans, M. C. W.
College/School:College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
Journal Name:Photosynthesis Research
Publisher:Springer
ISSN:0166-8595
ISSN (Online):1573-5079

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