The results of assembling the light-harvesting complexes in the cells of the purple sulfur bacterium Thiorhodospira (T.) sibirica strain Kir-3 while suppressing the biosynthesis of carotenoids with diphenylamine (DPA) were studied. LH2 complexes (B800-850 and B800-830) with different carotenoid composition were isolated from the cells obtained. Maximum inhibition of carotenoid biosynthesis (~90% of the control) was reached at an inhibitor concentration of 53.25 μM (9 mg/L). It was established that changes in the qualitative and quantitative composition of carotenoids do not affect the assembly of B800-830 and B800-850 complexes. It is assumed that, in the population of DPA-LH2 complexes from T. sibirica strain Kir-3, both the carotenoidless complexes and the complexes containing one or two carotenoid molecules can be assembled. These results support the hypothesis that carotenoids are not required for assembling B800-850 and B800-830 complexes.
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- The study examines how singlet oxygen affects light-harvesting complexes in various sulfur and nonsulfur photosynthetic bacteria, focusing on specific absorption spectra and carotenoid content.
- The results indicate that complete carotenoid presence in LH2 complexes enhances resistance to singlet oxygen, while other complexes show significant degradation of bacteriochlorophyll when exposed.
- The findings suggest that carotenoids' protective role in photosynthesis may not function as effectively in bacterial systems as previously thought, with reduced carotenoid levels surprisingly stabilizing certain complexes instead.
The LH2 Complexes (B800-850 and B800-830) Are Assembled in the Cells of the Sulfur Bacterium Thiorhodospira sibirica Strain Kir-3 without Carotenoids.
Dokl Biochem Biophys
July 2019
Institute of Basic Biological Problems of the Russian Academy of Sciences, Federal Research Center "Pushchino Scientific Center for Biological Research of Russian Academy of Sciences", 142290, Pushchino, Moscow oblast, Russia.
The results of assembling the light-harvesting complexes in the cells of the purple sulfur bacterium Thiorhodospira (T.) sibirica strain Kir-3 while suppressing the biosynthesis of carotenoids with diphenylamine (DPA) were studied. LH2 complexes (B800-850 and B800-830) with different carotenoid composition were isolated from the cells obtained.
View Article and Find Full Text PDFBiochemical and spectroscopic characterization of the B800-850 light-harvesting complex from Rhodobacter sulphidophilus and its B800-830 spectral form.
Biochemistry
August 1995
SBPM/DBCM CEA, Gif sur Yvette, France.
We demonstrate that the B800-830 spectral form of the B800-850 peripheral light-harvesting complex of Rhodobacter sulphidophilus, which is formed at low ionic strengths in the presence of the zwitterionic detergent LDAO, results from a local modification of the bacteriochlorophyll binding site and not the dissociation of the complex. This perturbation does not result in significant changes to the interactions between the pigments as studied by circular dichroism or fluorescence spectroscopy; however, modifications in the pigment binding sites are inferred from changes in the preresonance Raman spectrum. Specifically, an alteration of the hydrogen bonding of the 2-acetyl group of at least one of the bacteriochlorophyll groups that make up the 850 nm absorbing pair is observed.
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