Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.1 (nitrate reductase)
 3,728 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plasmid DNA carrying either the nitrate reductase (NR) gene or the argininosuccinate lyase gene as selectable markers and the corresponding Chlamydomonas reinhardtii mutants as recipient strains have been used to isolate regulatory mutants for nitrate assimilation by insertional mutagenesis. Identification of putative regulatory mutants was based on their chlorate sensitivity in the presence of ammonium. Among 8975 transformants, two mutants, N1 and T1, were obtained. Genetic characterization of these mutants indicated that they carry recessive mutations at two different loci, named Nrg1 and Nrg2. The mutation in N1 was shown to be linked to the plasmid insertion. Two copies of the nitrate reductase plasmid, one of them truncated, were inserted in the N1 genome in inverse orientation. In addition to the chlorate sensitivity phenotype in the presence of ammonium, these mutants expressed NR, nitrite reductase and nitrate transport activities in ammonium-nitrate media. Kinetic constants for ammonium (I4C-methylammonium) transport, as well as enzymatic activities related to the ammonium-regulated metabolic pathway for xanthine utilization, were not affected in these strains. The data strongly suggest that Nrg1 and Nrg2 are regulatory genes which specifically mediate the negative control exerted by ammonium on the nitrate assimilation pathway in C. reinhardtii.
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PMID:Isolation and characterization of two new negative regulatory mutants for nitrate assimilation in Chlamydomonas reinhardtii obtained by insertional mutagenesis. 870 50

Chlorophyll b is an ubiquitous accessory pigment in land plants, green algae, and prochlorophytes. Its biosynthesis plays a key role in the adaptation to various light environments. We isolated six chlorophyll b-less mutants by insertional mutagenesis by using the nitrate reductase or argininosuccinate lyase genes as tags and examined the rearrangement of mutant genomes. We found that an overlapping region of a nuclear genome was deleted in all mutants and that this encodes a protein whose sequence is similar to those of methyl monooxygenases. This coding sequence also contains putative binding domains for a [2Fe-2S] Rieske center and for a mononuclear iron. The results demonstrate that a chlorophyll a oxygenase is involved in chlorophyll b formation. The reaction mechanism of chlorophyll b formation is discussed.
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PMID:Chlorophyll a oxygenase (CAO) is involved in chlorophyll b formation from chlorophyll a. 977 May 52