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. 1999 Nov 9;96(23):13571-6.
doi: 10.1073/pnas.96.23.13571.

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

T Omata  1 , G D Price, M R Badger, M Okamura, S Gohta, T Ogawa
Affiliations

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

T Omata et al. Proc Natl Acad Sci U S A. .

Abstract

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.

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Figures

Figure 1
Figure 1
Comparison of the structures of the cmp-genomic region in WT and in the M42 (ΔcmpAB∷kanr) and CMP+ (PnirA∷cmpABCD) mutants of Synechococcus sp. strain PCC7942. The bar above the map shows the probe region used for Northern hybridization analysis. The open bars represent the antibiotic-resistance gene cassettes and the hatched bars show the location and orientation of the kanamycin-resistance gene (npt) and the sper gene (aad). The restriction endonuclease sites are abbreviated as follows: B, BglII; N, NcoI; P, PstI; Sa, SalI; Sp, SphI; and X, XbaI.
Figure 2
Figure 2
(A) Northern hybridization analysis of total RNA from Synechococcus, showing the effects of CO2 conditions on expression of the cmp operon. Synechococcus cells were grown with NO3− under high-CO2 conditions (2% CO2 in air) and transferred to low-CO2 conditions (0.005% CO2 in air). RNA samples (10 μg per lane) from WT (lanes 1 and 2) and the M42 mutant (lanes 3 and 4), extracted before (lanes 1 and 3) and 30 min after (lanes 2 and 4) the transfer, were denatured with formamide, separated on a 1.2% agarose-formaldehyde gel, transferred to a positive-charged nylon membrane (Hybond N+, Amersham), and hybridized with a 32P-labeled cmpC-specific probe. (B) Northern hybridization analysis of total RNA, showing the nitrogen-regulated expression of the cmp gene cluster under high CO2 in the CMP+ mutant. Synechococcus cells were grown with NH4+ and transferred to NO3−-containing medium under high-CO2 conditions. RNA samples (10 μg per lane) from WT (lanes 1 and 2) and CMP+ (lanes 3 and 4), extracted before (lanes 1 and 3) and 30 min after (lanes 2 and 4) the transfer, were analyzed as in A. (C) Immunoblotting analysis of CmpA in the plasma membrane of Synechococcus grown under constant C and nitrogen conditions. Plasma membrane samples from WT cells grown under high CO2 (lane 1) and low CO2 (lane 2) conditions in NO3−-containing medium and those from the CMP+ cells grown under high-CO2 conditions in NH4+- (lane 3) and NO3−- (lane 4) containing media were compared. Membrane proteins (5 μg per sample) were solubilized with SDS, fractionated by SDS/PAGE (10% gel), and electrotransferred to poly(vinylidene difluoride) membrane for immunostaining.
Figure 3
Figure 3
Uptake of HCO3− by high-CO2-grown cells (H) of WT (▾) and the CMP+ mutant (○, ●) and low-CO2-grown cells (▴) of WT (H) in the light. Cells were grown with NH4+ (○) or NO3− (●, ▾, ▴) as the nitrogen source. Uptake was initiated by illumination immediately after the addition of 100 μM H14CO3− to the cell suspensions. The amount of HCO3− taken up by the cells was determined from the total amount of 14C accumulated in the cell. Assays were done at 30°C and pH 9.0.
Figure 4
Figure 4
The rate of O2 evolution (A), net HCO3− uptake (B), and gross CO2 uptake (C) as a function of the HCO3− concentration in medium during steady-state photosynthesis in WT (▾) and the CMP+ mutant (○ and ●). Cells were grown under high-CO2 conditions at a light intensity of 250 μmol of photons m−2⋅s−1 with NH4+ (○) or NO3− (● and ▾) as the nitrogen source. Assays were done at 30°C and pH 8.2.
Figure 5
Figure 5
The rate of O2 evolution (A), net HCO3− uptake (B), and gross CO2 uptake (C) as a function of the HCO3− concentration in medium during steady-state photosynthesis in WT (□ and ■) and the M42 mutant (▵ and ▴). Cells were grown under high-CO2 (□ and ▵; H) and low-CO2 (■ and ▴; L) conditions at a light intensity of 90 μmol of photons m−2⋅s−1. Assays were done as described in Fig. 4.
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References

    1. Kaplan A, Schwarz R, Lieman-Hurwitz J, Ronen-Tarazi M, Reinhold L. In: The Molecular Biology of Cyanobacteria. Bryant D A, editor. Dordrecht, The Netherlands: Kluwer; 1994. pp. 469–485.
    1. Price G D, Sültemeyer D, Klughammer B, Ludwig M, Badger M R. Can J Bot. 1998;76:973–1002.
    1. Ogawa T. Proc Natl Acad Sci USA. 1991;88:4275–4279. - PMC - PubMed
    1. Sonoda M, Katoh H, Vermaas W, Schmetterer G, Ogawa T. J Bacteriol. 1998;180:3799–3803. - PMC - PubMed
    1. Bonfil D J, Tarazi-Ronen M, Sültemeyer D, Lieman-Hurwitz J, Schatz D, Kaplan A. FEBS Lett. 1998;430:236–240. - PubMed

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