Fluorescence of the various red antenna states in photosystem I complexes from cyanobacteria is affected differently by the redox state of P700

• Published in: Biochimica et biophysica acta 2011-11, Vol.1807 (11), p.1423-1431
• Main Authors: Schlodder, Eberhard, Hussels, Martin, Çetin, Marianne, Karapetyan, Navassard V., Brecht, Marc
• Format: Article
• Language: English
• Subjects: absorption; Arthrospira platensis; Bacterial Proteins - chemistry; chlorophyll; Chlorophyll - chemistry; Color; Cyanobacteria - chemistry; Cyanobacteria - metabolism; fluorescence; Fluorescence quenching; Light; Light-Harvesting Protein Complexes - chemistry; Long-wavelength antenna chlorophyll; Molecular Structure; Oxidation-Reduction; Photosystem I; Photosystem I Protein Complex - chemistry; Single molecule spectroscopy; Spectrometry, Fluorescence; Spirulina platensis; temperature; Thermosynechococcus elongatus; wavelengths
• ISSN: 0005-2728; 0006-3002; 1879-2650
• DOI: 10.1016/j.bbabio.2011.06.018

Photosystem I of cyanobacteria contains different spectral pools of chlorophylls called red or long-wavelength chlorophylls that absorb at longer wavelengths than the primary electron donor P700. We measured the fluorescence spectra at the ensemble and the single-molecule level at low temperatures in the presence of oxidized and reduced P700. In accordance with the literature, it was observed that the fluorescence is quenched by P700 +. However, the efficiency of the fluorescence quenching by oxidized P700 + was found to be extremely different for the various red states in PS I from different cyanobacteria. The emission of the longest-wavelength absorbing antenna state in PS I trimers from Thermosynechococcus elongatus (absorption maximum at 5 K: ≅ 719 nm; emission maximum at 5 K: ≅ 740 nm) was found to be strongly quenched by P700 + similar to the reddest state in PS I trimers from Arthrospira platensis emitting at 760 nm at 5 K. The fluorescence of these red states is diminished by more than a factor of 10 in the presence of oxidized P700. For the first time, the emission of the reddest states in A. platensis and T. elongatus has been monitored using single-molecule fluorescence techniques. ► Quenching by P700 +. ► Red/reddest antenna states. ► Reassignment of absorption bands.