Characterization of the different peripheral light-harvesting complexes from high- and low-light grown cells from Rhodopseudomonas palustris.
In this paper we demonstrate that the spectroscopically different peripheral light-harvesting complexes from Rhodopseudomonas palustris, strain 2.6.1, isolated from high- and low-light grown cells have widely differing bacteriochlorophyll a (BChl a) resonance Raman spectra in the high-frequency carbonyl region (1550-1750 cm-1). Complexes synthesized in low-light grown cells exhibit Raman spectra characteristic of B800-850 and B800-820 complexes, depending on the excitation conditions. The in vivo strategy for low-light adaptation in this bacterium is thus somewhat different from that generally encountered in the Rhodospirillaceae. In these bacteria, as typified by Rps. acidophila and Rps. cryptolactis, low-light conditions induce the synthesis of B800-820 only complexes in which the hydrogen bonds between the acetyl carbonyl and the B850 binding pocket are broken, inducing changes in the absorption properties of the monomeric bacteriochlorophylls. In the case of Rps. palustris, additional spectral effects occur due to the coupling of the electronic levels of the differently interacting dimers. The extensive use of differential alpha/beta-polypeptide expression [Tadros et al. (1993) Eur. J. Biochem. 217, 867-875] thus allows Rps. palustris to alter its BChl a binding site environments causing the observed spread of BChl a Qy transitions, ranging from 801 to 856 nm.
Gall
A
A
Section de Biophysique des Protéines et des Membranes, DBCM CEA and URA 2096 CNRS, Centre d'Etudes de Saclay, Gif-sur-Yvette, France.
Robert
B
B
D001429:Bacteriochlorophylls / Q000737:chemistry; D002338:Carotenoids / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002942:Circular Dichroism; D006860:Hydrogen Bonding; D008027:Light; D045342:Light-Harvesting Protein Complexes; D010455:Peptides / Q000737:chemistry; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D012241:Rhodopseudomonas / Q000737:chemistry* / Q000254:growth & development; D013050:Spectrometry, Fluorescence; D013059:Spectrum Analysis, Raman; D013696:Temperature
D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes; D010455:Peptides; D045322:Photosynthetic Reaction Center Complex Proteins; D002338:Carotenoids