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- Eriksson, M, et al.
(författare)
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Induction and regulation of expression of a low-CO2-induced mitochondrial carbonic anhydrase in Chlamydomonas reinhardtii
- 1998
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Ingår i: Plant Physiology. - 0032-0889 .- 1532-2548. ; 116:2, s. 637-641
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Tidskriftsartikel (refereegranskat)abstract
- The time course of and the influence of light intensity and light quality on the induction of a mitochondrial carbonic anhydrase (CA) in the unicellular green alga Chlamydomonas reinhardtii was characterized using western and northern blots. This CA was expressed only under low-CO2 conditions (ambient air). In asynchronously grown cells, the mRNA was detected 15 min after transfer from air containing 5% CO2 to ambient air, and the 21-kD polypeptide was detected on western blots after 1 h. When transferred back to air containing 5% CO2, the mRNA disappeared within 1 h and the polypeptide was degraded within 3 d. Photosynthesis was required for the induction in asynchronous cultures. The induction increased with light up to 500 mu mol m(-2) s(-1), where saturation occurred. In cells grown synchronously, however, expression of the mitochondrial CA was also detected in darkness. Under such conditions the expression followed a circadian rhythm, with mRNA appearing in the dark 30 min before the light was turned on. Algae left in darkness continued this rhythm for several days.
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| 2. |
- Hiltonen, Thomas, 1960-, et al.
(författare)
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Intracellular beta-carbonic anhydrase of the unicellular green alga Coccomyxa
- 1998
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Ingår i: Plant Physiology. - 0032-0889 .- 1532-2548. ; 117:4, s. 1341-1349
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Tidskriftsartikel (refereegranskat)abstract
- Carbonic anhydrase (CA) (EC 4.2.1.1) enzymes catalyze the reversible hydration of CO,, a reaction that is important in many physiological processes. We have cloned and sequenced a full length cDNA encoding an intracellular P-CA from the unicellular green alga Coccomyxa. Nucleotide sequence data show that the isolated cDNA contains an open reading frame encoding a polypeptide of 227 amino acids. The predicted polypeptide is similar to beta-type CAs from Escherichia coli and higher plants, with an identity of 26% to 30%. The Coccomyxa cDNA was overexpressed in E. coli, and the enzyme was purified and biochemically characterized. The mature protein is a homotetramer with an estimated molecular mass of 100 kD. The CO2-hydration activity of the Coccomyxa enzyme is comparable with that of the pea homolog. However, the activity of Coccomyxa CA is largely insensitive to oxidative conditions, in contrast to similar enzymes from most higher plants. Fractionation studies further showed that Coccomyxa CA is extrachloroplastic.
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