Characterization of the Nitrate-Nitrite Transporter of the Major Facilitator Superfamily (the nrtP Gene Product) from the Cyanobacterium Nostoc punctiforme Strain ATCC 29133
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The products of the <I>NpR1527</I> and <I>NpR1526</I> genes of the filamentous, diazotrophic, fresh-water cyanobacterium <I>Nostoc punctiforme</I> strain ATCC 29133 were identified as a nitrate transporter (NRT) and nitrate reductase (NR) respectively, by complementation of nitrate assimilation mutants of the cyanobacterium <I>Synechococcus elongatus</I> strain PCC 7942. While other fresh-water cyanobacteria, including <I>S. elongatus,</I> have an ATP-binding cassette (ABC)-type NRT, the NRT of <I>N. punctiforme</I> belongs to the major facilitator superfamily, being orthologous to the one found in marine cyanobacteria (NrtP). Unlike the ABC-type NRT, which transports both nitrate and nitrite with high affinity, <I>Nostoc</I> NrtP transported nitrate preferentially over nitrite. NrtP was distinct from ABC-type NRT also in its insensitivity to ammonium-promoted regulation at the post-translational level. The nitrate reductase of <I>N. punctiforme</I> was, on the other hand, inhibited upon addition of ammonium to medium, lending ammonium sensitivity to nitrate assimilation.
- Agricultural and Biological Chemistry
Agricultural and Biological Chemistry 70(11), 2682-2689, 2006-11-23
Japan Society for Bioscience, Biotechnology, and Agrochemistry