Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The gene (aoxA) coding for an L-amino acid oxidase (L-AOX) with high specificity for basic L-amino acids (L-arginine being the best substrate) in the cyanobacterium Synechococcus PCC 6301 has previously been identified, sequenced and analysed (Bockholt, R., Masepohl, M., Kruft, V., Wittmann-Liebold, B. and Pistorius, E.K. (1995) Biochim. Biophys. Acta 1264, 289-293). Here we report on the inactivation of the aoxA gene in the closely related Synechococcus PCC 7942 by interrupting the gene with a kanamycin resistance cassette from Tn5. The mutant called D6 has no detectable L-AOX activity and no detectable L-AOX protein. Characterization of the mutant showed that in contrast to Synechococcus PCC 7942 wild-type (WT) cells the mutant cells can not grow on L-arginine as sole N-source, suggesting that the L-AOX is essential for growth on L-arginine. Mutant cells can grow on nitrate or ammonium as N-source under photoautotropic conditions with a growth rate of about 75% of the WT rate. Under these conditions the photosynthetic O2 evolving activity is reduced by about the same amount, and the pigment content, especially the phycobiliprotein content, is much lower than in WT cells, indicating that the mutant suffers from some type of deficiency. Immunocytochemical investigations and extraction of the soluble proteins from periplasma after plasmolysing the cell wall gave evidence that the L-AOX is predominantly located in the periplasma with only a small amount being intracellularly located. A model of the possible function of the L-AOX in Synechococcus PCC 6301/7942 will be given.
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PMID:Construction and partial characterization of an L-amino acid oxidase-free Synechococcus PCC 7942 mutant and localization of the L-amino acid oxidase in the corresponding wild type. 865 60

The mitochondrial alternative oxidase (AOX) and the plastid terminal oxidase (PTOX) are two similar members of the membrane-bound diiron carboxylate group of proteins. AOX is a ubiquinol oxidase present in all higher plants, as well as some algae, fungi, and protists. It may serve to dampen reactive oxygen species generation by the respiratory electron transport chain. PTOX is a plastoquinol oxidase in plants and some algae. It is required in carotenoid biosynthesis and may represent the elusive oxidase in chlororespiration. Recently, prokaryotic orthologues of both AOX and PTOX proteins have appeared in sequence databases. These include PTOX orthologues present in four different cyanobacteria as well as an AOX orthologue in an alpha-proteobacterium. We used PCR, RT-PCR and northern analyses to confirm the presence and expression of the PTOX gene in Anabaena variabilis PCC 7120. An extensive phylogeny of newly found prokaryotic and eukaryotic AOX and PTOX proteins supports the idea that AOX and PTOX represent two distinct groups of proteins that diverged prior to the endosymbiotic events that gave rise to the eukaryotic organelles. Using multiple sequence alignment, we identified residues conserved in all AOX and PTOX proteins. We also provide a scheme to readily distinguish PTOX from AOX proteins based upon differences in amino acid sequence in motifs around the conserved iron-binding residues. Given the presence of PTOX in cyanobacteria, we suggest that this acronym now stand for plastoquinol terminal oxidase. Our results have implications for the photosynthetic and respiratory metabolism of these prokaryotes, as well as for the origin and evolution of eukaryotic AOX and PTOX proteins.
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PMID:Prokaryotic orthologues of mitochondrial alternative oxidase and plastid terminal oxidase. 1508 31