Photosynthetic electron transport in genetically altered chloroplasts. Progress report, June 15, 1992--June 15, 1993
We have generated and characterized the phenotypes of several photosystem II,D1 protein mutants in Chlamydomonas reinhardtii chloroplasts. The first set of mutants which we produced were at residue H195 on the D1 protein, adjacent to histidine -198 (H198), a putative ligand to the redox active chlorophyll special pair, P680. Conservative amino acid replacements at H195 had little effect on electron transfer whereas non-conservative replacements had significant effects on electron transfer processes, particularly rates of transfer from Z to P680. In contrast, histidine 190 (H190) mutants were unable to evolve oxygen, had reduced manganese content, slower rates of charge transfer from Z to P680 and lacked the A{sub t} thermoluminescence band. These results suggested that H190 may be a redox active histidine residue required for photoligation of manganese into the water oxidizing complex. EPR studies demonstrated that H190 does not H-bond to Z. This is in contrast to the H190 residue of the D2 protein which does H-bond to the redox active tyrosine, D. These are the first results which identify a specific histidine residue as potentially being redox active in photosystem II and have implications for the structure of the water oxidizing complex.
- Research Organization:
- The Ohio State Univ., Columbus, OH (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-92ER20076
- OSTI ID:
- 10164783
- Report Number(s):
- DOE/ER/20076-1; ON: DE93017200
- Resource Relation:
- Other Information: PBD: Jun 1993
- Country of Publication:
- United States
- Language:
- English
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