Thermoluminescence evidence for light‐induced oxidation of tyrosine and histidine residues in manganese‐depleted photosystem II particles

Abstract

In the therrnoluminesccncc (TL) glow curve of photosystem 11, particles depleted of manganese, a tyrosinc modifier. 7-chloro&nitrobcnz-2-oxa-I ,3-diazolc (NBD) abolishes the TL band appearing around -55°C (TL_,,). Addition of a histidinc modifier, diethylpyrocarbonatc results in the disappearance of the band peaking around -30°C (TL-J. NBD trcatmcnt also abolish& the EPR signal &, of oxidized tyrosine donor, Y,, and inhibits the electron transport from diphcnylcarbaddc to 2,6_dichlorophcnol-indophcnol. It is concluded that the TL_5S and TLLW bands can bc assigned IO oxidized tyrosinc (Y,') and histidinc (His') residues, rcspcctivcly. which participate in clcctron transfer from manganese to the reaction center of chlorophyll, P680'.

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“…Site directed mutagenesis of Chlamydomonas reinhardtii showed that the replacement of His195 in the vicinity of TyrZ did not influence the peak position of the AT band, while the conversion of His190 residue to phenylalanine completely abolished this band (Kramer et al 1994). This is in good agreement with the earlier observation that the tyrosine modifier NBD (7-chloro-4-nitrobenz-2-oxa-1,3-diazole) had no influence on the AT band (Allakhverdiev et al 1992). …”

“…This assumption also seems to be supported by the work of Jegerschöld et al (1995) If the above mentioned effects of Cu-poisoning are really the consequence of Tyrz inhibition, we must get very similar results by adding the Tyrz modifier NBD (Deters et al 1975;Allakhverdiev et al 1992) to functional thylakoids. As shown in Figure 4.…”

“…In our further experiments the relationship between the A and AT bands were tested by applying the histidine modifier DEPC (Allakhverdiev et al 1992;Ehrenberg et al 1976;Hedge et al 1993). As show in Figure 5, both the A and AT band could be abolished by the increasing concentrations of DEPC.…”

“…In TRIS-washed thylakoids or TRIS-treated BBY particles, the A band corresponding to S3QA− is replaced by the AT band (Koike et al 1986) which originates from HisCQA− charge recombination (Ono and Inoue 1991;Allakhverdiev et al 1992). In our further experiments the relationship between the A and AT bands were tested by applying the histidine modifier DEPC (Allakhverdiev et al 1992;Ehrenberg et al 1976;Hedge et al 1993).…”

“…Comparative studies of the EPR signal IIfast and TL characteristics as well as treatment of thylakoids with the histidine modifier diethyl pyrocarbonate (DEPC) led to the conclusion that the AT band originated from HisCQA− recombination (Ono and Inoue 1991;Allakhverdiev et al 1992). Site directed mutagenesis of Chlamydomonas reinhardtii showed that the replacement of His195 in the vicinity of TyrZ did not influence the peak position of the AT band, while the conversion of His190 residue to phenylalanine completely abolished this band (Kramer et al 1994).…”