Biomedical subjects

T Omata

Publications and source records attributed to T Omata.

At least 19 recordsLinked to original sources

PubMed2000

Bicarbonate binding activity of the CmpA protein of the cyanobacterium Synechococcus sp. strain PCC 7942 involved in active transport of bicarbonate.

The cmpABCD operon of the cyanobacterium Synechococcus sp. strain PCC 7942 encodes an ATP-binding cassette transporter involved in HCO(3)(-) uptake. The three genes, cmpBCD, encode membrane components of an ATP-binding cassette transporter, whereas cmpA encodes a 42-kDa cytoplasmic membrane protein, which is 46.5% identical to the membrane-anchored substrate-binding protein of the nitrate/nitrite transporter. Equilibrium dialysis analysis using H(14)CO(3)(-) showed that a truncated CmpA protein lacking the N-terminal 31 amino acids, expressed in Escherichia coli cells as a histidine-tagged soluble protein, specifically binds inorganic carbon (CO(2) or HCO(3)(-)). The addition of the recombinant CmpA protein to a buffer caused a decrease in the concentration of dissolved CO(2) because of the binding of inorganic carbon to the protein. The decrease in CO(2) concentration was accelerated by the addition of carbonic anhydrase, indicating that HCO(3)(-), but not CO(2), binds to the protein. Mass spectrometric measurements of the amounts of unbound and bound HCO(3)(-) in CmpA solutions containing low concentrations of inorganic carbon revealed that CmpA binds HCO(3)(-) with high affinity (K(d) = 5 microm). A similar dissociation constant was obtained by analysis of the competitive inhibition of the CmpA protein on the carboxylation of phosphoenolpyruvate by phosphoenolpyruvate carboxylase at limiting concentrations of HCO(3)(-). These findings showed that the cmpA gene encodes the substrate-binding protein of the HCO(3)(-) transporter.

ATP-Binding Cassette Transporters↗

PubMed2000

Synthesis and Physical Properties of Sterically Congested Cycloalkenes, 1,2-Di-tert-butyl-3,3,5,5-tetramethylcyclopentene and 1,2-Di-tert-butyl-3,3,6,6-tetramethylcyclohexene.

Two sterically congested cycloalkenes (9 and 10), congeners of tetra-tert-butylethylene, were synthesized and characterized. Oxidation of the bicyclic 1,3-dithietane 8 with dimethyldioxirane (DMD) gave the endo,endo-disulfoxide 13, thermal isomerization of which to the endo,exo-disulfoxide 15 followed by oxidation with DMD gave the trioxide 18. Heating 18 in refluxing 1,3-dimethyl-2-imidazolidinone furnished 1,2-di-tert-butyl-3,3,5,5-tetramethylcyclopentene (9) in 69% yield by a 2-fold extrusion process. The reaction of the 1,6-diketone dihydrazone 23 with Se(2)Cl(2) gave the selenadiazoline 34 and the 1,3-diselenetane 35. Heating 34 at 115-130 degrees C gave 1,2-di-tert-butyl-3,3,6,6-tetramethylcyclohexene (10), a "didehydro" derivative of tetra-tert-butylethylene, in 43% yield. The C=C bond in 10 is strained in degree comparable to those of most strained alkenes reported so far.

Journal Article↗

PubMed2000

Motor dynamics encoding in the rostral zone of the cat cerebellar flocculus during vertical optokinetic eye movements.

The complex spike (CS) and simple spike (SS) activities of Purkinje cells in the rostral zone of the cerebellar flocculus were recorded in alert cats during optokinetic responses (OKR) elicited by a stimulus sequence consisting of a constant-speed visual pattern movement in one direction for 1 s and then in the opposite direction for 1 s. The quick-phase-free trials were selected. Ninety-eight cells were identified as rostral zone cells by the direction-selective CS activity that was modulated during vertical but not horizontal stimuli. In most of the majority population (88 cells), with an increasing CS firing rate during upward OKR and an increasing SS rate during downward OKR, the inverse dynamics approach was successful and the time course of the SS rate was reconstructed (mean coefficient of determination, 0.70 and 0.72 during upward and downward stimuli, respectively) by a linear weighted superposition of the eye acceleration, velocity, position, and constant terms, at a given time delay (mean 10 ms) from the unit response to the eye-movement response. Standard regression coefficient (SRC) analysis revealed that the contribution of the velocity term (mean SRC 0.98 for upward and 0.80 for downward) to regression was dominant over acceleration (mean SRC 0.018 and 0.058) and position (-0.14 and -0.12) terms. The velocity coefficient during upward stimuli (6.6 spikes/s per degree/s) was significantly (P<0.01) larger than that during downward stimuli (4.9 spikes/s per degree/s). In most of the minority population (10 cells), with both CS and SS firing rates increasing during upward OKR, the inverse dynamics approach was not successful. It is concluded that 1) in the cat rostral zone Purkinje cells, in which the preferred direction is upward for CS and downward for SS, eye velocity and acceleration information is encoded in SS firing to counteract the viscosity and inertia forces, respectively, on the eye during vertical OKR; 2) the eye position information encoded in SS firing is inappropriate for counteracting the elastic force; 3) encoding of eye velocity information during upward OKR is quantitatively different from that during downward OKR: SS firing modulation is larger for upward than for downward OKR of the same amplitude; and 4) encoding of motor dynamics is obscure in cells in which the preferred direction is upward for both CS and SS.

Acceleration↗

PubMed2000

Usefulness and pitfalls of intraoperative spinal motor evoked potential recording by direct cortical electrical stimulation.

OBJECTIVE: The aim of this study is to investigate the usefulness and problems with spinal motor evoked potential (MEP) recording, especially the reasons for failed recording. We report our personal experience over the last 8 years in patients with lesions adjacent to the primary motor cortex. METHODS: MEP records of 50 consecutive patients were retrospectively reviewed. MEP was recorded by a catheter electrode inserted in the cervical epidural space. Stimulation electrodes were placed on the cortical surface during surgery. SEP recording was also performed in 29 of 50 patients. RESULTS: MEP was obtained in 40 cases, and SEP was recorded in all 29 cases. The central sulcus was identified in 93% of patients in whom both MEP and SEP were performed, whereas in only 86% of patients who underwent only MEP. The main reason for MEP failure were inadequate exposure of the motor cortex, pre-existing hemiparesis and technical errors. Postoperative deterioration of motor function was closely related to intra-operative MEP changes. CONCLUSION: MEP is a useful tool to determine the motor cortex and to predict postoperative motor function. However, precise pre-operative craniotomy planning and combination with intra-operative SEP is essential to reduce the MEP failure.

Adolescent↗

PubMed2000

Effects of chondroitin sulfate-C on articular cartilage destruction in murine collagen-induced arthritis.

The effects of chondroitin sulfate-C (CAS 25322-46-7, Chondroitin ZS Tab) on type II collagen (CII)-induced arthritis (CIA) in mice were evaluated. DBA/1J mice were immunized with bovine CII emulsified in Freund's complete adjuvant, followed by a booster injection 21 days later. Chondroitin sulfate-C at doses of 100, 300 and 1000 mg/kg was administered orally once daily beginning 14 days before initial immunization. An arthritis index and hind paw edema were examined from day 0 to day 49, when the mice were killed by ether anesthesia for histopathological examination. The delayed-type hypersensitivity (DTH) reaction, serum anti-CII antibody titer, and histopathologic characteristics of both synovitis and destruction of articular cartilage were analyzed. Both the arthritis index and the serum anti-CII antibody titer were reduced by treatment with chondroitin sulfate-C in a dose-dependent manner. Chondroitin sulfate-C (1000 mg/kg) significantly inhibited hind paw edema, synovitis and destruction of the articular cartilage, but not DTH reaction.

Animals↗

PubMed2000

Effects of ZNC-2381, a new oral compound, on several hepatic injury models and on hepatocellular apoptosis in mice and rats.

The hepatoprotective effect of ZNC-2381 (1-(4-aminophenyl) methyl-3-(3-nitrophenyl)-1,3-dihydroimidazo[4,5-b]pyridine-2-one), a novel 2-one dihydroimidazopyridine derivative, has been evaluated in several experimental models of hepatic injury. In mice, oral ZNC-2381, administered at doses of 3, 10 or 30 mgkg(-1), 1 h before induction of hepatic injury with concanavalin A, dose-dependently inhibited increases in serum alanine aminotransferase (ALT) activity. Apoptosis of liver cells, as indicated by DNA fragmentation (nucleosome assay) and DNA-ladder formation (electrophoresis), was also inhibited dose-dependently. ZNC-2381 dose-dependently inhibited concanavalin A-induced increases in serum tumour necrosis factor (TNF)-alpha levels, and TNF-alpha mRNA expression in the liver. Oral ZNC-2381 also dose-dependently inhibited increases in serum ALT activity in mice with hepatic injury induced by Propionibacterium acnes and a bacterial lipopolysaccharide (LPS) or D-galactosamine-LPS, and in rats with D-galactosamine-induced hepatic injury. These results indicate that oral ZNC-2381 inhibits cytokine (TNF-alpha) production and cytokine-related hepatocellular apoptosis, and might thus prevent different types of hepatic injury.

Alanine Transaminase↗

PubMed2000

[A case of famotidine-induced aseptic meningitis].

We reported a 50-year-old woman with a history of mixed connective tissue disease. She had two episodes of meningitis-like symptoms after taking famotidine and tiquizium bromide for treatment of gastric ulcer. From CSF findings (elevated pressure, increase of protein, polymorphonuclear pleocytosis, negative culture) and result of famotidine challenge test, we diagnosed her as a drug induced aseptic meningitis. Because she had taken tiquizium bromide several times previously without any side effects, we concluded that famotidine was a causative drug. She was recovered without sequelae within a few days following cessation of these drugs. This is the first report of H2-blocker induced aseptic meningitis. When we encounter a patient with aseptic meningitis who presents polymorphonuclear pleocytosis in CSF, we should suspect drug induced aseptic meningitis and take a history of drug medication including H2-blocker.

Anti-Ulcer Agents↗

PubMed1999

Identification of an ATP-binding cassette transporter involved in bicarbonate uptake in the cyanobacterium Synechococcus sp. strain PCC 7942.

Exposure of cells of cyanobacteria (blue-green algae) grown under high-CO(2) conditions to inorganic C-limitation induces transcription of particular genes and expression of high-affinity CO(2) and HCO(3)(-) transport systems. Among the low-CO(2)-inducible transcription units of Synechococcus sp. strain PCC 7942 is the cmpABCD operon, encoding an ATP-binding cassette transporter similar to the nitrate/nitrite transporter of the same cyanobacterium. A nitrogen-regulated promoter was used to selectively induce expression of the cmpABCD genes by growth of transgenic cells on nitrate under high CO(2) conditions. Measurements of the initial rate of HCO(3)(-) uptake after onset of light, and of the steady-state rate of HCO(3)(-) uptake in the light, showed that the controlled induction of the cmp genes resulted in selective expression of high-affinity HCO(3)(-) transport activity. The forced expression of cmpABCD did not significantly increase the CO(2) uptake capabilities of the cells. These findings demonstrated that the cmpABCD genes encode a high-affinity HCO(3)(-) transporter. A deletion mutant of cmpAB (M42) retained low CO(2)-inducible activity of HCO(3)(-) transport, indicating the occurrence of HCO(3)(-) transporter(s) distinct from the one encoded by cmpABCD. HCO(3)(-) uptake by low-CO(2)-induced M42 cells showed lower affinity for external HCO(3)(-) than for wild-type cells under the same conditions, showing that the HCO(3)(-) transporter encoded by cmpABCD has the highest affinity for HCO(3)(-) among the HCO(3)(-) transporters present in the cyanobacterium. This appears to be the first unambiguous identification and description of a primary active HCO(3)(-) transporter.

ATP-Binding Cassette Transporters↗

PubMed1999

Postoperative oblique sagittal MR imaging of microvascular decompression for hemifacial spasm.

Pre-operative and postoperative oblique sagittal gradient-echo magnetic resonance (MR) imaging was used to evaluate micro-vascular decompression of the facial nerves in 26 patients with hemifacial spasm. The pre-operative MR images were divided into two groups as follows: 22 images in Group I, clear imaging of a high-intensity line and/or spot at the root exit zone (REZ) of the facial nerve; and 4 in Group II, and unreliable image around the REZ. Surgery found that the causative vessel was the vertebral artery (VA) in 9 cases and the anterior inferior cerebellar artery (AICA) or the posterior inferior cerebellar artery (PICA) in 13 cases in Group I, and the AICA or the PICA in the 4 cases in Group II. Postoperative MR imaging showed clear decompression as the high-intensity line and/or spot completely separated from the REZ by a low- and/or iso- intensity area in 9 cases of VA compression repositioned to the petrous dura matter, in 11 cases of PICA or AICA compression treated by shredded Teflon pledgets in Group I and in 3 cases in Group II. Postoperative MR imaging showed an incomplete separation of any high-intensity line and/or spot in the REZ in 2 cases of PICA or AICA compression in Group I and in one in Group II. The outcome was excellent in 22 of 23 cases with clear decompression, and in 1 of 3 cases of unclear decompression. Hemifacial spasm persisted in 3 cases. Oblique sagittal gradient-echo MR imaging is a useful method for postoperative follow-up which can demonstrate changes around the REZ of the facial nerve if hemifacial spasm recurs.

Arteries↗

PubMed1999

Age-depending effects of methotrexate treatment on systemic bone turnover in experimental adjuvant arthritis.

Adjuvant arthritis was induced in rats in the growth stage (aged 6 weeks) and those in the mature stage (aged 4 months), and changes in the systemic bone turnover and the effects of methotrexate (MTX, CAS 133073-73-1) were compared. After induction of adjuvant arthritis, the paw edema ratio and the urinary deoxypyridinoline (u-Dpy) level increased in both age groups. No marked changes were observed in the serum osteocalcin (s-OC) level in either group. In the 6-week-old rats, arthritis completely inhibited the bone mass, and strength of the femur and lumbar vertebral body. The 4-month-old rats showed more marked changes than the 6-week-old rats in the bone mass and strength of the lumbar, vertebral body. MTX administration (0.05, 0.1 and 0.2 mg/kg/day) resulted in significant dose-dependent inhibition of arthritis-induced changes, and the effects of MTX were similar between the two age groups. MTX was useful at each age. These results suggest that 4-month-old rats with arthritis are more appropriate as a model for evaluation of drugs for bone metabolic turnover in human chronic rheumatoid arthritis.

Absorptiometry, Photon↗

PubMed1999

Effects of chondroitin sulfate-C on bradykinin-induced proteoglycan depletion in rats.

Depletion of the proteoglycan content of articular cartilage was induced by injecting bradykinin (30-300 mumol/l, 50 microliters/knee) into the left knee articular cavities of rats 3 times a day for 2 days. The degree of the reduction in the intensity of histopathological safranin O staining was used as an index of proteoglycan depletion. Bradykinin reduced the cartilage proteoglycan contents of the knee joints of non-injected limbs in a dose-dependent manner and at 300 mumol/l markedly reduced these contents, but evoked no inflammatory changes. The extent of the reduction of the cartilage proteoglycan contents induced by bradykinin injection depended on the dose and injection frequency. Chondroitin sulfate-C (CAS 25322-46-7, Chondroitin ZS Tab) (30-1,000 mg/kg/day) administered orally to rats for 14 days inhibited the bradykinin-induced proteoglycan depletion of the articular cartilage in a dose-dependent manner. These results suggest that a reduction of the proteoglycan content of cartilage, like that associated with osteoarthritis, was induced by injecting bradykinin into the knee articular cavities of rats and chondroitin sulfate-C protected against this effect.

Animals↗

PubMed1999

Motor dynamics encoding in cat cerebellar flocculus middle zone during optokinetic eye movements.

We investigated the relationship between eye movement and simple-spike (SS) frequency of Purkinje cells in the cerebellar flocculus middle zone during the optokinetic response (OKR) in alert cats. The OKR was elicited by a sequence of a constant-speed visual pattern movement in one direction for 1 s and then in the opposite direction for 1 s. Quick-phase-free trials were selected. Sixty-six cells had direction-selective complex spike (CS) activity that was modulated during horizontal (preferring contraversive) but not vertical stimuli. The SS activity was modulated during horizontal OKR, preferring ipsiversive stimuli. Forty-one cells had well-modulated activity and were suitable for the regression model. In these cells, an inverse dynamics approach was applied, and the time course of the SS rate was reconstructed, with mean coefficient of determination 0.76, by a linear weighted superposition of the eye acceleration (mean coefficient, 0.056 spikes/s per deg/s(2)), velocity (5.10 spikes/s per deg/s), position (-2.40 spikes/s per deg), and constant (mean 34.3 spikes/s) terms, using a time delay (mean 11 ms) from the unit response to the eye response. The velocity and acceleration terms contributed to the increase in the reconstructed SS rates during ipsilateral movements, whereas the position term contributed during contralateral movements. The standard regression coefficient analyses revealed that the contribution of the velocity term (mean coefficient 0.81) was predominant over the acceleration (0.03) and position (-0.17) terms. Forward selection analysis revealed three cell types: Velocity-Position-Acceleration type (n = 27): velocity, position, and acceleration terms are significant (P < 0.05); Velocity-Position type (n = 12): velocity and position terms are significant; and Velocity-Acceleration type (n = 2): velocity and acceleration terms are significant. Using the set of coefficients obtained by regression of the response to a 5 deg/s stimulus velocity, the SS rates during higher (10, 20, and 40 deg/s) stimulus velocities were successfully reconstructed, suggesting generality of the model. The eye-position information encoded in the SS firing during the OKR was relative but not absolute in the sense that the magnitude of the position shift from the initial eye position (0 deg/s velocity) contributed to firing rate changes, but the initial eye position did not. It is concluded that 1) the SS firing frequency in the cat middle zone encodes the velocity and acceleration information for counteracting the viscosity and inertia forces respectively, during short-duration horizontal OKR and 2) the apparent position information encoded in the SS firing is not appropriate for counteracting the elastic force during the OKR.

Animals↗

PubMed1999

D-galactosamine-induced mouse hepatic apoptosis: possible involvement with tumor necrosis factor, but not with caspase-3 activity.

We investigated whether tumor necrosis factor (TNF) and caspase-3 activity are involved in the induction of hepatocellular apoptosis in D-galactosamine (D-GalN)-induced hepatotoxicity in mice. Acute hepatotoxicity was induced by the intraperitoneal injection of D-GalN into female BALB/c mice. D-GalN (0.75-3.0 g/kg) increased the serum glutamate pyruvate transaminase (s-GPT) activity and the percentage of liver DNA fragmentation, an indicator of hepatotoxicity, after 48 h, in a dose-dependent manner. Furthermore, after D-GalN (3.0 g/kg) administration, increased liver DNA fragmentation was detected biochemically at 24 h, then increased s-GPT activity accompanied by increased liver DNA fragmentation was observed after 48 h. The serum TNF (s-TNF) level and the TNF mRNA expression in the liver after D-GalN (3.0 g/kg, i.p.) administration were examined by an ELISA kit and reverse transcription polymerase chain reaction (RT-PCR), respectively, to investigate the relation between the s-GPT activity and liver DNA fragmentation. The s-TNF level and TNF mRNA expression in the liver after D-GalN (3.0 g/kg) administration were detected earlier than liver DNA fragmentation, then increased with time. However, there was almost no association of caspase-3 activity with the increase in liver DNA fragmentation. Increases in the s-TNF level, TNF mRNA expression and the percentage of DNA fragmentation in the liver and s-GPT activity were inhibited by dexamethasone (Dex; 0.4-2.5 mg/kg, i.p.) in a dose-dependent manner. Based on these findings, it was considered that the intracellular apoptosis signal in D-GalN-induced hepatotoxicity in mice did not depend on caspase-3 activity, and that other signals mediated by TNF may be involved.

Animals↗

PubMed1998

Independence of carbon and nitrogen control in the posttranslational regulation of nitrate transport in the cyanobacterium Synechococcus sp. strain PCC 7942.

Nitrate transport by Synechococcus sp. strain PCC 7942 cells was inhibited by ammonium and by inhibitors of CO2 fixation. Ammonium assimilation inhibitors, such as L-methionine D,L-sulfoximine, were known to prevent the negative effects of ammonium and of inhibitors of CO2 fixation on nitrate uptake, leading to propose that CO2 fixation was required to counteract the feed-back inhibition of nitrate assimilation. In NR-less mutants, L-methionine D,L-sulfoximine prevented the negative effects of ammonium on nitrate transport, but not always prevented those of inhibiting CO2 fixation. The carboxy-terminal domain of the NrtC subunit of the nitrate transporter has recently been identified as a regulatory domain involved in N-control. The mutant strain NC2, constructed by deleting the 3' portion of nrtC, showed high nitrate transport activity insensitive to ammonium but sensitive to inhibitors of CO2 fixation. These findings indicate that the C-control and the N-control of nitrate transport are independent at both the physiological and the molecular level.

Biological Transport↗

PubMed1998

Prediction of vertebral artery compression in patients with hemifacial spasm using oblique sagittal MR imaging.

To discriminate between the various compressing vessels of the facial nerves in patients with hemifacial spasm, pre-operative oblique sagittal gradient-echo MR imaging was performed. Forty-two patients underwent pre-operative MR imaging and microvascular decompression. The MR images were divided according to findings into three groups as follows: Group A, a thick and/or long high-intensity line along the root exit zone (REZ) of the facial nerve; Group B, a thin and/or short high-intensity line along the REZ; and Group C, an unreliable image around the REZ. Fifteen images were classified as Group A, 19 as Group B, and 8 as Group C. In Group A, vertebral artery (VA) compression was confirmed intra-operatively in 12 cases and posterior inferior cerebellar artery (PICA) or anterior inferior cerebellar artery (AICA) compression in 3. In Group B, PICA or AICA compression was confirmed intra-operatively in all cases. In Group C, PICA or AICA compression was confirmed intra-operatively in 7 cases and no compression in one. In all cases of VA compression of the facial nerve, the oblique sagittal gradient-echo images demonstrated a thick and/or long high intensity line along the REZ. Oblique sagittal gradient-echo MR imaging is a useful preoperative planning aid, which can predict the possibility of VA compression prior to microvascular decompression for hemifacial spasm.

Facial Nerve↗

PubMed1998

Promoters of the phycocyanin gene clusters of the cyanobacterium Synechococcus sp. strain PCC 7942.

The cyanobacterium Synechococcus sp. strain PCC 7942 has duplicated phycocyanin subunit gene clusters cpcB1A1 and cpcB2A2, which are identical to each other and to those of Synechococcus sp. strain PCC 6301 (Anacystis nidulans). Nucleotide sequences of the 428 and 286 bases of the 5' non-coding regions of the cpcB1A1 and cpcB2A2 clusters, respectively, of strain PCC 7942 were identical to those of strain PCC 6301. As in strain PCC 6301, cpcB1A1 yielded two major transcripts of 1.4 and 1.3 kb and cpcB2A2 yielded a single transcript of 1.3 kb in strain PCC 7942. Thus, the structure and expression of cpcBA gene clusters in the two strains are essentially the same. Using bacterial luciferase encoded by luxAB as a reporter, cpcB1A1 was shown to have two promoters corresponding to the two major transcripts. Luminescence from the Synechococcus reporter strains carrying the fusions of the cpcBA promoters to luxAB showed circadian oscillation. Similar to the promoter of psbA1 encoding the D1 protein of PSII, the two cpcB1A1 promoters and the cpcB2A2 promoter showed the peak of activity at the end of the subjective day and the trough at the end of the subjective night.

Base Sequence↗

PubMed1998

cis-acting sequences required for NtcB-dependent, nitrite-responsive positive regulation of the nitrate assimilation operon in the cyanobacterium Synechococcus sp. strain PCC 7942.

There are three binding sites for NtcA (nirI, nirII, and nirIII), the global nitrogen regulator of cyanobacteria, in the DNA region between the two divergently transcribed operons (nirA and nirB operons) involved in nitrate assimilation in Synechococcus sp. strain PCC 7942. Using the luxAB reporter system, we showed that nirI and nirIII, which are located 23 bp upstream from the -10 promoter element of nirA and nirB, respectively, are required for induction by nitrogen depletion of the nirA and nirB operons, respectively. The induction of nirA operon transcription was a prerequisite for the nitrite-responsive positive regulation of the transcription by NtcB, a LysR-type protein. The NtcA-binding site nirII, located in the middle of the nirA-nirB intergenic region, and a potential binding site for a LysR-type protein (TGCAN5TGCA; designated L1), located between nirI and nirII, were required for the nitrite-responsive, NtcB-dependent enhancement of nirA operon transcription. Although the requirement for the L1 site was consistent with the involvement of the LysR family protein NtcB in transcriptional regulation, NtcB did not bind to the nirA regulatory region in vitro in the presence of nitrite and NtcA, suggesting the involvement of some additional factor(s) in the regulation. An L1-like inverted repeat with the consensus sequence TGCN7GCA was conserved in the nirA promoter region of cyanobacteria, being centered at position -23 with respect to the NtcA-binding site corresponding to nirI, which suggested the common occurrence of nitrite-responsive regulation of the nitrate assimilation operon among cyanobacteria.

Bacterial Proteins↗

PubMed1998

Nitrite-specific active transport system of the cyanobacterium Synechococcus sp. strain PCC 7942.

Studies on the nitrite uptake capability of a mutant of Synechococcus sp. strain PCC 7942 lacking the ATP-binding cassette-type nitrate-nitrite-bispecific transporter revealed the occurrence of a nitrite-specific active transport system with an apparent Km (NO2-) of about 20 microM. Similar to the nitrate-nitrite-bispecific transporter, the nitrite-specific transporter was reversibly inhibited by ammonium in the medium.

Biological Transport, Active↗