Mutant trimers of light-harvesting complex II exhibit altered pigment content and spectroscopic features.
Mutants of plant light-harvesting complex II (LHC-II) were produced by refolding the complex in vitro from bacterially expressed apoprotein and purified pigments by a method which yields native-like LHC-II in a single step. Amino acid residues known from the structure of the complex [Kühlbrandt, W., et al. (1994) Nature 367, 614-621] to bind chlorophyll (Chl) were replaced with nonbinding residues by site-directed mutagenesis. Recombinant monomeric and trimeric pigment-protein complexes were separated by density gradient centrifugation, and their pigment composition was determined. Six out of nine mutants formed trimers with Chl a:Chl b ratios and Chl contents which suggested they were lacking one Chl a or b per polypeptide. In this way, the identities of Chls a1, a2, a3, b5, and b6 were confirmed as Chl a or b, respectively, whereas Chl b3 in the structure was found to be a Chl a. Absorption and fluorescence emission spectra of the mutant lacking Chl a2 indicated a central role for this Chl in energy transfer to the reaction center.
Rogl
H
H
Max-Planck-Institut für Biophysik, Frankfurt am Main, Germany.
Kühlbrandt
W
W
D001216:Asparagine / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D002338:Carotenoids / Q000032:analysis; D002734:Chlorophyll / Q000235:genetics* / Q000378:metabolism*; D018698:Glutamic Acid / Q000235:genetics; D005973:Glutamine / Q000235:genetics; D045342:Light-Harvesting Protein Complexes; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D018532:Pisum sativum; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D017510:Protein Folding; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D011994:Recombinant Proteins; D005973:Glutamine; D002734:Chlorophyll; D002338:Carotenoids; D018698:Glutamic Acid; D001216:Asparagine