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PMID:8083164

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Citation

Kozliak, EI, Guilloton, MB, Gerami-Nejad, M, Fuchs, JA and Anderson, PM (1994) Expression of proteins encoded by the Escherichia coli cyn operon: carbon dioxide-enhanced degradation of carbonic anhydrase. J. Bacteriol. 176:5711-7

Abstract

Cyanase catalyzes the reaction of cyanate with bicarbonate to give 2CO2. The cynS gene encoding cyanase, together with the cynT gene for carbonic anhydrase, is part of the cyn operon, the expression of which is induced in Escherichia coli by cyanate. The physiological role of carbonic anhydrase is to prevent depletion of cellular bicarbonate during cyanate decomposition due to loss of CO2 (M.B. Guilloton, A.F. Lamblin, E. I. Kozliak, M. Gerami-Nejad, C. Tu, D. Silverman, P.M. Anderson, and J.A. Fuchs, J. Bacteriol. 175:1443-1451, 1993). A delta cynT mutant strain was extremely sensitive to inhibition of growth by cyanate and did not catalyze decomposition of cyanate (even though an active cyanase was expressed) when grown at a low pCO2 (in air) but had a Cyn+ phenotype at a high pCO2. Here the expression of these two enzymes in this unusual system for cyanate degradation was characterized in more detail. Both enzymes were found to be located in the cytosol and to be present at approximately equal levels in the presence of cyanate. A delta cynT mutant strain could be complemented with high levels of expressed human carbonic anhydrase II; however, the mutant defect was not completely abolished, perhaps because the E. coli carbonic anhydrase is significantly less susceptible to inhibition by cyanate than mammalian carbonic anhydrases. The induced E. coli carbonic anhydrase appears to be particularly adapted to its function in cyanate degradation. Active cyanase remained in cells grown in the presence of either low or high pCO2 after the inducer cyanate was depleted; in contrast, carbonic anhydrase protein was degraded very rapidly (minutes) at a high pCO2 but much more slowly (hours) at a low pCO2. A physiological significance of these observations is suggested by the observation that expression of carbonic anhydrase at a high pCO2 decreased the growth rate.

Links

PubMed PMC196775

Keywords

Carbon Dioxide; Carbon-Nitrogen Lyases; Carbonic Anhydrases/analysis; Carbonic Anhydrases/biosynthesis; Carbonic Anhydrases/genetics; Carbonic Anhydrases/metabolism; Cyanates/pharmacology; Cytosol/chemistry; Enzyme Induction; Escherichia coli/drug effects; Escherichia coli/enzymology; Escherichia coli/genetics; Gene Expression Regulation, Bacterial/physiology; Genetic Complementation Test; Humans; Lyases/analysis; Lyases/biosynthesis; Lyases/genetics; Lyases/metabolism; Mutation/physiology; Operon/genetics

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

ECOLI:CYNS

part_of

GO:0005737: cytoplasm

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete


See also

References

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