Characterization of a phycoerythrin without alpha-subunits from a unicellular red alga.
We describe here the spectral and biochemical properties of a novel biliprotein belonging to the phycoerythrin family, purified from the phycobilisome of a unicellular red alga, Rhodella reticulata strain R6. This biliprotein is assembled from a unique beta-type subunit, chloroplast-encoded, whose hexameric or dodecameric aggregates are stabilized by unusually large linkers (87 and 60 kDa) encoded by the nuclear genome. Although each beta-type subunit bears two phycoerythrobilins and one phycocyanobilin per chain, the linker polypeptides are non-chromophorylated. The apoprotein of the beta-subunit of the R. reticulata R6 phycoerythrin is specified by a monocistronic rpeB chloroplast gene that is split into three exons. We discuss the relationships between R6 beta-phycoerythrin and the previously published polypeptide sequences, the structural consequences due to the absence of an alpha-subunit, and its evolutionary implications.
Thomas
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JC
Laboratoire de Photorégulation et Dynamique des Membranes Végétales, CNRS, Unité de Recherche Associée 1810, GDR 1002, Ecole Normale Supérieure, 46 rue d'Ulm, 75 230 Paris Cedex 05, France. jcthomas@biologie.ens.fr
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D000595:Amino Acid Sequence; D001483:Base Sequence; D002736:Chloroplasts / Q000378:metabolism; D002848:Chromatography, DEAE-Cellulose; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005091:Exons; D007438:Introns; D008969:Molecular Sequence Data; D045524:Phycobilisomes; D010799:Phycoerythrin / Q000737:chemistry* / Q000235:genetics; D015183:Restriction Mapping; D000461:Rhodophyta / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence
D018076:DNA, Complementary; D045524:Phycobilisomes; D010799:Phycoerythrin