Involvement of the C-terminal Domain of an ATP-binding Subunit in the Regulation of the ABC-type Nitrate/Nitrite Transporter of the Cyanobacterium Synechococcus sp. Strain PCC 7942

Kobayashi, Masaki; Rodríguez, Rafael Moreno; Lara, Catalina; Omata, Tatsuo

doi:10.1074/jbc.272.43.27197

Cited by 63 publications

(77 citation statements)

References 35 publications

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“…In S. elongatus, but not in Synechocystis, an excess amount of ammonium inhibited nitrate reductase activity even when the protein was expressed. 32) Our observation of the interaction with NblR might explain the phenomenon as an inhibitory effect of NblR on the activity of NarB, because no nblR ortholog exists in the Synechocystis genome. Further studies on these interactions are underway to determine how nutrient-deprivation signals modify the function of the NblR transcriptional factor.…”

Section: Discussionmentioning

confidence: 86%

NblR Is a Novel One-Component Response Regulator in the CyanobacteriumSynechococcus elongatusPCC 7942

Katô

Chibazakura

Yoshikawa

2008

Bioscience, Biotechnology, and Biochemistry

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Section: Discussionmentioning

confidence: 86%

NblR Is a Novel One-Component Response Regulator in the CyanobacteriumSynechococcus elongatusPCC 7942

Katô

Chibazakura

Yoshikawa

2008

Bioscience, Biotechnology, and Biochemistry

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“…Ammonium, when available, is the preferred nitrogen source over nitrate because it can be directly incorporated into cellular biomass without expending valuable reducing equivalents (13). In wild-type cells, ammonium not only inhibits nitrate uptake but also halts nitrate utilization by inhibiting nitrate reductase (6). Mutants lacking the solute-binding domain of NrtC continue nitrate uptake in the presence of ammonium but can no longer reduce nitrate because of the inhibition of nitrate reductase (6).…”

Section: Discussionmentioning

confidence: 99%

“…NrtD consists of a single ATPase domain. In contrast, NrtC contains both an ATPase domain and a C-terminal solute-binding domain that shares 50% amino acid sequence similarity with NrtA, and is required for the ammonium-mediated inhibition of nitrate transport (5,6). Aside from the homologous transporter for bicarbonate, CmpABCD, there are no other known examples of ABC transporters that have an ATPase͞solute-binding fusion component.…”

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confidence: 99%

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Atomic structure of a nitrate-binding protein crucial for photosynthetic productivity

Koropatkin

Pakrasi

Smith

2006

Proc. Natl. Acad. Sci. U.S.A.

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Cyanobacteria, blue-green algae, are the most abundant autotrophs in aquatic environments and form the base of all aquatic food chains by fixing carbon and nitrogen into cellular biomass. The single most important nutrient for photosynthesis and growth is nitrate, which is severely limiting in many aquatic environments particularly the open ocean. It is therefore not surprising that NrtA, the solute-binding component of the high-affinity nitrate ABC transporter, is the single-most abundant protein in the plasma membrane of these bacteria. Here, we describe the structure of a nitrate-specific receptor, NrtA from Synechocystis sp. PCC 6803, complexed with nitrate and determined to a resolution of 1.5 Å. NrtA is significantly larger than other oxyanion-binding proteins, representing a previously uncharacterized class of transport proteins. From sequence alignments, the only other solute-binding protein in this class is CmpA, a bicarbonate-binding protein. Therefore, these organisms created a solute-binding protein for two of the most important nutrients: inorganic nitrogen and carbon. The electrostatic charge distribution of NrtA appears to force the protein off the membrane while the flexible tether facilitates the delivery of nitrate to the membrane pore. The structure not only details the determinants for nitrate selectivity in NrtA but also the bicarbonate specificity in CmpA. Nitrate and bicarbonate transport are regulated by the cytoplasmic proteins NrtC and CmpC, respectively. Interestingly, the residues lining the ligand binding pockets suggest that they both bind nitrate. This implies that the nitrogen and carbon uptake pathways are synchronized by intracellular nitrate and nitrite.ABC transporter ͉ carbon ͉ nitrogen assimilation ͉ regulation T he single most important nutrient for photosynthesis and growth is nitrate, which is severely limiting in many aquatic environments such as the open ocean (1, 2). Therefore, the cyanobacteria have developed a high-affinity ABC transport system that is composed of four polypeptides ( Fig. 1): a highaffinity periplasmic solute-binding lipoprotein (NrtA), an integral membrane permease (NrtB), a cytoplasmic ATPase (NrtD), and a unique ATPase͞solute-binding fusion protein (NrtC) that regulates transport (3). NrtA binds both nitrate and nitrite (K d ϭ 0.3 mM) and is necessary for cell survival when nitrate is the primary nitrogen source (4). The role of NrtA is to scavenge nitrate͞nitrite from the periplasm for delivery to the membrane permease, NrtB. The passage of solute through the transmembrane pore is linked to ATP hydrolysis by NrtC and NrtD. NrtD consists of a single ATPase domain. In contrast, NrtC contains both an ATPase domain and a C-terminal solute-binding domain that shares 50% amino acid sequence similarity with NrtA, and is required for the ammonium-mediated inhibition of nitrate transport (5, 6). Aside from the homologous transporter for bicarbonate, CmpABCD, there are no other known examples of ABC transporters that have an ATPase͞solute-binding fusion co...

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“…Ammonium reversibly inhibits nitrate assimilation (Ohmori et al, 1977;Flores et al, 1980). This involves the C-terminus of NrtC-one of the ATPase components of the nitrate transporterand its truncation relieves the ammonium inhibition (Kobayashi et al, 1997). Nitrite uptake by marine Synechococcus WH7803 was repressed by ammonium additions (Lindell et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

Decoupling of ammonium regulation and ntcA transcription in the diazotrophic marine cyanobacterium Trichodesmium sp. IMS101

2011

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Nitrogen (N) physiology in the marine cyanobacterium Trichodesmium IMS101 was studied along with transcript accumulation of the N-regulatory gene ntcA and of two of its target genes: napA (nitrate assimilation) and nifH (N 2 fixation). N 2 fixation was impaired in the presence of nitrite, nitrate and urea. Strain IMS101 was capable of growth on these combined N sources at o2 lM but growth rates declined at elevated concentrations. Assimilation of nitrate and urea was impaired in the presence of ammonium. Whereas ecologically relevant N concentrations (2-20 lM) suppressed growth and assimilation, much higher concentrations were required to affect transcript levels. Transcripts of nifH accumulated under nitrogen-fixing conditions; these transcript levels were maintained in the presence of nitrate (100 lM) and ammonium (20 lM). However, nifH transcript levels were below detection at ammonium concentrations 420 lM. napA mRNA was found at low levels in both N 2 -fixing and ammonium-utilizing filaments, and it accumulated in filaments grown with nitrate. The positive effect of nitrate on napA transcription was abolished by ammonium additions of 4200 lM. This effect was restored upon addition of the glutamine synthetase inhibitor L-methionin-DL-sulfoximine. Surprisingly, ntcA transcript levels remained high in the presence of ammonium, even at elevated concentrations. These findings indicate that ammonium repression is decoupled from transcriptional activation of ntcA in Trichodesmium IMS101.

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Involvement of the C-terminal Domain of an ATP-binding Subunit in the Regulation of the ABC-type Nitrate/Nitrite Transporter of the Cyanobacterium Synechococcus sp. Strain PCC 7942

Cited by 63 publications

References 35 publications

NblR Is a Novel One-Component Response Regulator in the CyanobacteriumSynechococcus elongatusPCC 7942

NblR Is a Novel One-Component Response Regulator in the CyanobacteriumSynechococcus elongatusPCC 7942

Atomic structure of a nitrate-binding protein crucial for photosynthetic productivity

Decoupling of ammonium regulation and ntcA transcription in the diazotrophic marine cyanobacterium Trichodesmium sp. IMS101

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