title: Evolutionary relationship of psbA genes from cyanobacteria, cyanelles and plastids.
abstract: The psbA gene is part of the reaction center of photosystem II in cyanobacteria and the plastids of higher plants. Its primary sequence is highly conserved among all species investigated so far and its sequence shows homologies with the L and M subunits of the reaction center of photosynthetic bacteria. We have analyzed the psbA homolog from a eukaryotic alga, Cyanophora paradoxa, where the gene is encoded on cyanelle DNA. These cyanelles are surrounded by a murein sacculus and resemble cyanobacteria in many other characteristics, although they are genuine organelles that functionally replace plastids. Analysis of the gene revealed a psbA protein identical in length (360 codons) with the cyanobacterial counterpart. The overall sequence identity is, however, more pronounced between cyanelle psbA and the shorter (353 amino acids) psbA product found in higher plants. These data strongly support the postulated bridge position of cyanelles between chloroplasts and free-living cyanobacteria.
authors.affiliation: Institut für Allgemeine Biochemie, Universität Wien, Austria.
authors.forename: I
authors.initials: I
authors.lastname: Janssen
authors.forename: J
authors.initials: J
authors.lastname: Jakowitsch
authors.forename: C B
authors.initials: CB
authors.lastname: Michalowski
authors.forename: H J
authors.initials: HJ
authors.lastname: Bohnert
authors.forename: W
authors.initials: W
authors.lastname: Löffelhardt
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D005075:Biological Evolution; D002734:Chlorophyll / Q000235:genetics*; D000458:Cyanobacteria / Q000235:genetics*; D004271:DNA, Fungal / Q000235:genetics; D005796:Genes; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012689:Sequence Homology, Nucleic Acid
chemical_list: D004271:DNA, Fungal; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll