Phycoerythrins of the oxyphotobacterium Prochlorococcus marinus are associated to the thylakoid membrane and are encoded by a single large gene cluster |
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Authors: | Hess Wolfgang R Steglich Claudia Lichtlé Christiane Partensky Frédéric |
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Institution: | (1) Department of Biology, Humboldt-University, Chausseestrasse 117, 10115 Berlin, Germany;(2) Laboratoire de Photorégulation et Dynamique des Membranes Végétales, Ecole Normale Supérieure, CNRS URA 1810, 46 rue d'Ulm, Paris Cedex 05, France;(3) Station Biologique, CNRS, INSU et Université Pierre et Marie Curie, BP 74, 29682 Roscoff Cedex, France |
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Abstract: | An intrinsic divinyl-chlorophyll a/b antenna and a particular form of phycobiliprotein, phycoerythrin (PE) III, coexist in the marine oxyphotobacterium Prochlorococcus marinus CCMP 1375. The genomic region including the cpeB/A operon of P. marinus was analysed. It encompasses 10 153 nucleotides that encode three structural phycobiliproteins and at least three (possibly five) different polypeptides analogous to cyanobacterial or red algal proteins involved either in the linkage of subunits or the synthesis and attachment of chromophoric groups. This gene cluster is part of the chromosome and is located within a distance of less than 110 kb from a previously characterized region containing the genes aspA-psbA-aroC. Whereas the Prochlorococcus phycobiliproteins are characterized by distinct deletions and amino acid replacements with regard to analogous proteins from other organisms, the gene arrangement resembles the organization of phycobiliprotein genes in some other cyanobacteria, in particular marine Synechococcus strains. The expression of two of the Prochlorococcus polypeptides as recombinant proteins in Escherichia coli allowed the production of individual homologous antisera to the Prochlorococcus and PE subunits. Experiments using these sera show that the Prochlorococcus PEs are specifically associated to the thylakoid membrane and that the protein level does not significantly vary as a function of light irradiance or growth phase. |
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Keywords: | cyanobacteria immunogold labelling light-harvesting complexes photosynthesis phycobilins phytoplankton |
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