Trichloroacetate affects the EPR Signal IIslow and Signal I in the thylakoid ofChlamydomonas reinhardtii
One electron paramagnetic resonance (EPR) signal, named Signal IIslow, originates from the oxidized Tyrosine 160 (YD) of D2 polypeptide of photosystem II reaction center. After adding high concentration trichloroacetate (TCA) to theChlamydomonas reinhardtii thylakoid suspension, this signal was abolished in a minute. Treatment of TCA also removes a few of polypeptides, including three extrinsic polypeptides of oxygen-evolving complex, from the thylakoid membrane. Based upon the analysis of the microenvironment around YD with a three-dimensional model, it is indicated that relatively high hydrophobicity of this microenvironment may be the essential prerequisite for TCA to affect YD. It has been observed that TCA treatment also retards the decay of the Signal 1, produced by the oxidized reaction center chlorophyll dimer (P700+) of photosystem I.
Keywordsthylakoid YD EPR trichloroacetate (TCA) three-dimensional model
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