Inorganic Fe 2+ formation upon Fe-S protein thermodestruction in the membranes of thermophilic cyanobacteria: Mössbauer spectroscopy study

• Published in: FEBS letters 1999-04, Vol.450 (1), p.135-138
• Main Authors: Kaurov, Yu.N., Novakova, A.A., Davletshina, L.N., Aleksandrov, A.Yu, Khval’kovskaya, E.A., Semin, B.K., Belevich, N.P., Ivanov, I.I., Rubin, A.B.
• Format: Article
• Language: English
• Subjects: Fe-S center; Iron; Mössbauer spectroscopy; Photosystem I; Thermodestruction; Thermophilic cyanobacterium
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/S0014-5793(99)00485-8

A model description of the Mössbauer spectrum (80 K) of native membranes of the thermophilic cyanobacterium Synechococcus elongatus is suggested on the basis of the known values of quadrupole splitting (Δ E Q) and isomer shift ( δ Fe) for the iron-containing components of the photosynthetic apparatus. Using this approach, we found that heating the membranes at 70–80 K results in a decrease of doublet amplitudes belonging to F X, F A, F B and ferredoxin and simultaneous formation of a new doublet with Δ E Q=3.10 mm/s and δ Fe=1.28 mm/s, typical of inorganic hydrated forms of Fe 2+. The inhibition of electron transfer via photosystem I to oxygen, catalyzed by ferredoxin, occurs within the same range of temperatures. The data demonstrate that the processes of thermoinduced Fe 2+ formation and distortions in the photosystem I electron transport in the membranes are interrelated and caused mainly by the degradation of ferredoxin. The possible role of Fe 2+ formation in the damage of the photosynthetic apparatus resulting from heating and the action of other extreme factors is discussed.