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- Nucleotide and deduced polypeptide sequences of the photosyn...Nucleotide and deduced polypeptide sequences of the photosynthetic reaction-center, B870 antenna, and flanking polypeptides from R. capsulata
Cell, Volume 37, Issue 3, 1 July 1984, Pages 949-957
Douglas C. Youvan, Edward J. Bylina, Marie Alberti, Helmut Begusch and John E. Hearst
SummaryThe complete nucleotide sequence (8867 bp) and the deduced polypeptide sequence are given for 11 proteins from the photosynthetic gene cluster of R. capsulata (46 kb), including the photosynthetic reaction-center L, M, and H subunits and the B870α and B870β polypeptides (light-harvesting I). These polypeptides bind bacteriochlorophyll, bacteriopheophytin, carotenoids, and quinones that are involved in the primary light reactions of photosynthesis. Hydropathy plots indicate that the L and M subunits are transmembrane proteins that may cross the membrane five times, while the H subunit has only one hydrophobic section near the amino terminus, which may be transmembrane. The L and M subunits are homologous over their entire length and have a high degree of homology with the Q protein from photosystem II of higher plants. An additional six genes were identified that may have some unknown role in bioenergetics since only mutations that affect the differentiation of the photosynthetic apparatus are known to map to this gene cluster.
Summary | PDF (1053 kb) - Spectroscopy of Individual Light-Harvesting 2 Complexes of R...Spectroscopy of Individual Light-Harvesting 2 Complexes of Rhodopseudomonas acidophila: Diagonal Disorder, Intercomplex Heterogeneity, Spectral Diffusion, and Energy Transfer in the B800 Band
Biophysical Journal, Volume 78, Issue 3, 1 March 2000, Pages 1570-1577
A.M. van Oijen, M. Ketelaars, J. Köhler, T.J. Aartsma and J. Schmidt
AbstractThis paper reports a detailed spectroscopic study of the B800 absorption band of individual light-harvesting 2 (LH2) complexes of the photosynthetic purple bacterium at 1.2K. By applying single-molecule detection techniques to this system, details and properties can be revealed that remain obscured in conventional ensemble experiments. For instance, from fluorescence-excitation spectra of the individual complexes a more direct measure of the diagonal disorder could be obtained. Further spectral diffusion phenomena and homogeneous linewidths of individual bacteriochlorophyll a (BChl a) molecules are observed, revealing valuable information on excited-state dynamics. This work demonstrates that it is possible to obtain detailed spectral information on individual pigment-protein complexes, providing direct insight into their electronic structure and into the mechanisms underlying the highly efficient energy transfer processes in these systems.
Abstract | Full Text | PDF (271 kb) - Regulatory factors controlling photosynthetic reaction cente...Regulatory factors controlling photosynthetic reaction center and light-harvesting gene expression in Rhodobacter capsulatus
Cell, Volume 68, Issue 5, 6 March 1992, Pages 945-954
Michael W. Sganga and Carl E. Bauer
SummaryMost species of photosynthetic bacteria synthesize their photosynthetic apparatus only under conditions of reduced oxygen tension. To a large extent, this phenomenon is dependent upon anaerobic induction of photosynthesis gene expression. Here we report an example of a regulatory gene, , that is involved in transactivating anaerobic expression of the photosynthetic apparatus. We show that RegA is itself responsible for differential induction of light-harvesting and reaction center gene expression relative to operons for photopigment biosynthesis. Surprisingly, strains disrupted for were found to retain normal photosynthetic growth capabilities under high light intensities. We further show that photosynthetic growth in the absence of transactivating structural gene expression is a consequence of the superoperonal organization of the photosynthetic gene cluster.
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Copyright © 1984 The Biophysical Society. All rights reserved.
Biophysical Journal, Volume 45, Issue 2, 455-461, 1 February 1984
doi:10.1016/S0006-3495(84)84168-5
Research Article
Light saturation curves and quantum yields in reaction centers from photosynthetic bacteria
H.M. Cho, L.J. Mancino and R.E. Blankenship
Abstract
Reaction centers isolated from the photosynthetic bacterium Rhodopseudomonas sphaeroides R-26 mutant were irradiated with laser pulses of variable energy and the amount of photooxidation of the primary electron donor bacteriochlorophyll was measured. The resultant light saturation curve fits an exponential function and not a hyperbolic or hyperbolic tangent function. Analysis using either a Poisson statistical model or a simple kinetic model predicts an exponential light saturation curve in the limit where the light pulse is long relative to any transient intermediate states. The absolute quantum yield of photochemistry was found to be 0.98, utilizing the entire light saturation curve. Distortions from the simple exponential light saturation behavior are predicted when very short laser pulses are used.
