Replacement of Tyrosine D with Phenylalanine Affects the Normal Proton Transfer Pathways for the Reduction of P680+ in Oxygen-Evolving Photosystem II Particles from Chlamydomonas
| Autor: | C. Jeans, M. J. Schilstra, N. Ray, S. Husain, J. Minagawa, J. H. A. Nugent, D. R. Klug |
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| Rok vydání: | 2002 |
| Předmět: |
Free Radicals
Photosystem II Phenylalanine Photosynthetic Reaction Center Complex Proteins Static Electricity Photosynthesis Photochemistry Photosystem I Biochemistry Spinacia oleracea Animals Plant Proteins biology Chemistry Algal Proteins Chlamydomonas Electron Spin Resonance Spectroscopy Photosystem II Protein Complex food and beverages P680 biology.organism_classification Kinetics Mutagenesis Insertional Membrane Amino Acid Substitution Energy Transfer Thylakoid Tyrosine Spinach Protons Oxidation-Reduction Chlamydomonas reinhardtii |
| Zdroj: | Biochemistry. 41:15754-15761 |
| ISSN: | 1520-4995 0006-2960 |
| Popis: | We have probed the electrostatics of P680(+) reduction in oxygenic photosynthesis using histidine-tagged and histidine-tagged Y(D)-less Photosystem II cores. We make two main observations: (i) that His-tagged Chlamydomonas cores show kinetics which are essentially identical to those of Photosystem II enriched thylakoid membranes from spinach; (ii) that the microsecond kinetics, previously shown to be proton/hydrogen transfer limited [Schilstra et al. (1998) Biochemistry 37, 3974-3981], are significantly different in Y(D)-less Chlamydomonas particles when compared with both the His-tagged Chlamydomonas particles and the spinach membranes. The oscillatory nature of the kinetics in both Chlamydomonas samples is normal, indicating that S-state cycling is unaffected by either the histidine-tagging or the replacement of tyrosine D with phenylalanine. We propose that the effects on the proton-coupled electron transfers of P680(+) reduction in the absence of Y(D) are likely to be due to pK shifts of residues in a hydrogen-bonded network of amino acids in the vicinity of Y(Z). Tyrosine D is 35 A from Y(Z) and yet has a significant influence on proton-coupled electron transfer events in the vicinity of Y(Z). This finding emphasizes the delicacy of the proton balance that Photosystem II has to achieve during the water splitting process. |
| Databáze: | OpenAIRE |
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