TEMPERATURE-DEPENDENCE OF THE S1-]S2 TRANSITION IN THE OXYGEN-EVOLVING COMPLEX OF PHOTOSYSTEM-II STUDIED BY FT-IR SPECTROSCOPY

The temperature dependence of the single-turnover redox reaction on the electron-donor side of Photosystem II (PS II) has been investigated by measuring light-induced FTIR difference spectra of DCMU-treated PS Il membranes at various temperatures of 80-240 K. The negative band at 1404 cm-1 in the difference spectra exhibited the same temperature dependence as the S2 formation in the oxygen-evolving center previously determined by EPR spectroscopy (De Paula, J.C., Innes, J.B. and Brudvig, G.W. (1985) Biochemistry 24, 8114-8120). This observation strongly supports our previous assignment of the 1404 cm-1 band to the structural change of proteins upon the S1 --> S2 transition (Noguchi, T., Ono, T. and Inoue, Y. (1992) Biochemistry 31, 5953-5956). The temperature dependence of the 1660 cm-1 band due to cytochrome b559 (Cyt b559) oxidation has shown a complementary relationship to that of the 1404 cm-1 band, consistent with the view that the oxidation of Cyt b559 competes with the S2 formation on the electron-donor side of PS II. The present FTIR data also suggest that the structural difference between the two S2 states exhibiting the g = 4.1 EPR signal and the multiline signal is not very large as far as the protein moiety around the Mn cluster responsible for the 1404 cm-1 band is concerned.