TY - JOUR
T1 - Reconstitution of the bacterial core light-harvesting complexes of Rhodobacter sphaeroides and Rhodospirillum rubrum with isolated α- and β-polypeptides, bacteriochlorophyll a, and carotenoid
AU - Davis, Christine M.
AU - Bustamante, Peggy L.
AU - Loach, Paul A.
PY - 1995/3/17
Y1 - 1995/3/17
N2 - Methodology has been developed to reconstitute carotenoids and bacteriochlorophyll a with isolated light-harvesting complex I (LHI) polypeptides of both Rhodobacter sphaeroides and Rhodospirillum rubrum. Reconstitution techniques first developed in this laboratory using the LHI polypeptides of R. rubrum, R. sphaeroides, and Rhodobacter capsulatus reproduced bacteriochlorophyll a spectral properties characteristic of LHI complexes lacking carotenoids. In this study, carotenoids are supplied either as organic-solvent extracts of chromatophores or as thin-layer chromatography or high performance liquid chromatography-purified species. The resulting LHI complexes exhibit carotenoid and bacteriochlorophyll a spectral properties characteristic of native LHI complexes of carotenoid-containing bacteria. Absorption and circular dichroism spectra support the attainment of a native-like carotenoid environment in the reconstituted LHI complexes. For both R. sphaeroides-and R. rubrum-reconstituted systems, fluorescence excitation spectra reveal appropriate carotenoid to bacteriochlorophyll a energy-transfer efficiencies based on comparisons with the in vivo systems. In the case of R. rubrum reconstitutions, carotenoids afford protection from photodynamic degradation. Thus, carotenoids reconstituted into LHI exhibit spectral and functional characteristics associated with native pigments. Heterologous reconstitutions demonstrate the applicability of the developed assay in dissecting the molecular environment of carotenoids in light-harvesting complexes.
AB - Methodology has been developed to reconstitute carotenoids and bacteriochlorophyll a with isolated light-harvesting complex I (LHI) polypeptides of both Rhodobacter sphaeroides and Rhodospirillum rubrum. Reconstitution techniques first developed in this laboratory using the LHI polypeptides of R. rubrum, R. sphaeroides, and Rhodobacter capsulatus reproduced bacteriochlorophyll a spectral properties characteristic of LHI complexes lacking carotenoids. In this study, carotenoids are supplied either as organic-solvent extracts of chromatophores or as thin-layer chromatography or high performance liquid chromatography-purified species. The resulting LHI complexes exhibit carotenoid and bacteriochlorophyll a spectral properties characteristic of native LHI complexes of carotenoid-containing bacteria. Absorption and circular dichroism spectra support the attainment of a native-like carotenoid environment in the reconstituted LHI complexes. For both R. sphaeroides-and R. rubrum-reconstituted systems, fluorescence excitation spectra reveal appropriate carotenoid to bacteriochlorophyll a energy-transfer efficiencies based on comparisons with the in vivo systems. In the case of R. rubrum reconstitutions, carotenoids afford protection from photodynamic degradation. Thus, carotenoids reconstituted into LHI exhibit spectral and functional characteristics associated with native pigments. Heterologous reconstitutions demonstrate the applicability of the developed assay in dissecting the molecular environment of carotenoids in light-harvesting complexes.
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U2 - 10.1074/jbc.270.11.5793
DO - 10.1074/jbc.270.11.5793
M3 - Article
C2 - 7890709
AN - SCOPUS:0028927242
SN - 0021-9258
VL - 270
SP - 5793
EP - 5804
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 11
ER -