The heme oxygenase gene (pbsA) in the red alga Rhodella violacea is discontinuous and transcriptionally activated during iron limitation.
Heme oxygenase (HO) catalyzes the opening of the heme ring with the release of iron in both plants and animals. In cyanobacteria, red algae, and cryptophyceae, HO is a key enzyme in the synthesis of the chromophoric part of the photosynthetic antennae. In an attempt to study the regulation of this key metabolic step, we cloned and sequenced the pbsA gene encoding this enzyme from the red alga Rhodella violacea. The gene is located on the chloroplast genome, split into three distant exons, and is presumably expressed by a trans-splicing mechanism. The deduced polypeptide sequence is homologous to other reported HOs from organisms containing phycobilisomes (Porphyra purpurea and Synechocystis sp. strain PCC 6803) and, to a lesser extent, to vertebrate enzymes. The expression is transcriptionally activated under iron deprivation, a stress condition frequently encountered by algae, suggesting a second role for HO as an iron-mobilizing agent in photosynthetic organisms.
Richaud
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Laboratoire de Photorégulation et Dynamique des Membranes Végétales, Centre National de la Recherche Scientifique, Unité de Recherche Associée 1810, GDR 1002, Ecole normale supérieure, 46 rue d'Ulm, 75230 Paris, France. richaud@biologie.ens.fr
Zabulon
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002645:Chickens; D002736:Chloroplasts / Q000201:enzymology; D000458:Cyanobacteria / Q000235:genetics; D017931:DNA Primers; D005091:Exons; D015971:Gene Expression Regulation, Enzymologic; D017343:Genes, Plant; D015698:Genomic Library; D006419:Heme Oxygenase (Decyclizing) / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D006801:Humans; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology; D008969:Molecular Sequence Data; D045524:Phycobilisomes; D016133:Polymerase Chain Reaction; D015183:Restriction Mapping; D000461:Rhodophyta / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D017931:DNA Primers; D045524:Phycobilisomes; D007501:Iron; D006419:Heme Oxygenase (Decyclizing)