Molecular study of a light-harvesting apoprotein of Giraudyopsis stellifer (Chrysophyceae).
We have isolated a gene from a library of nuclear DNA for a chlorophyll a/c-binding protein (named Cac for chl a/c by analogy with Cab for chl a/b) of a chromophyte alga, Giraudyopsis stellifer, and sequenced it. The comparison of the deduced amino acid sequence with other chl a/c- and chl a/b-binding protein sequences shows that structural and functional features, i.e. the arrangement 'en X' of the two A and B transmembrane helices and the putative chl a-binding sites, are shared by both Chlorophyta and Chromophyta. Moreover, in contrast to Chlorophyta, a very strong identity is found among Chromophyta in the C helix suggesting a major function associated to this specific region. Nevertheless, the primary structure of the apoprotein does not seem affected by the pigment composition in Chromophyta. As in the few other examples currently known, we confirm that the cac genes are nuclear-encoded and are part of a multigenic family. Northern blots, performed on poly(A)+ mRNA from G: stellifer, give evidence that the cac gene is light-induced at a transcriptional level and that no expression can be observed in the dark.
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Laboratoire de Photorégulation et Dynamique des Membranes Végétales, Ecole Normale Supérieure, Centre National de la Recherche Scientifique URA 1810, Paris, France.
Lichtl
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D000595:Amino Acid Sequence; D001483:Base Sequence; D056890:Eukaryota / Q000235:genetics*; D008027:Light; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D005810:Multigene Family; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; C088752:fucoxanthin-, chlorophyll a-c-containing protein