Abstract
The activity of ferredoxin: NADP+ reductase (FNR) was found to decline to approximately 20% maximal levels with little or no loss in enzyme levels when cultures of the cyanobacterium Anabaena variabilis were maintained in the stationary phase of growth. Re-activation of enzyme activity occurred when cells were diluted into either fresh or re-utilized media and illuminated. This reversible de-activation/re-activation process was found, in vivo, to be dependent on the intensity of light illuminating the cells. The de-activated form of FNR was purified to homogeneity and exhibited the same molecular mass, isoelectric-focusing pattern and N-terminal amino acid sequence as the native form. Both de-activated and native FNR preparations each exhibited three reactive thiol groups on denaturation in urea; however, the rate of reaction with Ellman's reagent was much faster with the de-activated form than with the native form. Both preparations contain a single disulphide bond. Upon reduction of the disulphide bond in either form of the enzyme, the five reactive thiol groups exhibited identical reactivities in the presence of urea. Steady-state kinetic analysis of the de-activated form showed a marked increase in Km values for NADPH in diaphorase assays and an increase in Km for ferredoxin in the ferredoxin-mediated reduction of cytochrome c. No significant difference in kcat. was observed in comparison of the de-activated with the native form in any of the above assays; however, the de-activated form did exhibit a lower kcat. value in the transhydrogenase assay. The de-activated form of FNR bound ferredoxin with a 16-fold lower affinity than the native enzyme. These data suggest that the de-activation of FNR in vivo in response to low light intensity involves an alteration in protein structure, possibly via an intramolecular thiol disulphide interchange, which influences the interaction of the enzyme with its substrates.
Full text
PDF





Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- BARTLETT G. R. Phosphorus assay in column chromatography. J Biol Chem. 1959 Mar;234(3):466–468. [PubMed] [Google Scholar]
- Berzborn R. 2. Uberlösliche und unlösliche Chloroplasten-Antigene. Nachweis der Ferredoxin-NADP-Reduktase in der Oberfläche des Chloroplasten-Lamellarsystes mit Hilfe spezifischer Antikörper. Z Naturforsch B. 1968 Aug;23(8):1096–1104. [PubMed] [Google Scholar]
- Buchanan B. B. The ferredoxin/thioredoxin system: a key element in the regulatory function of light in photosynthesis. Bioscience. 1984 Jun;34(6):378–383. [PubMed] [Google Scholar]
- Böhme H. On the role of ferredoxin and ferredoxin-NADP+ reductase in cyclic electron transport of spinach chloroplasts. Eur J Biochem. 1977 Jan;72(2):283–289. doi: 10.1111/j.1432-1033.1977.tb11251.x. [DOI] [PubMed] [Google Scholar]
- Cavallini D., Graziani M. T., Dupré S. Determination of disulphide groups in proteins. Nature. 1966 Oct 15;212(5059):294–295. doi: 10.1038/212294a0. [DOI] [PubMed] [Google Scholar]
- Coles C. J., Edmondson D. E., Singer T. P. Reversible inactivation of L-amino acid oxidase. Properties of the three conformational forms. J Biol Chem. 1977 Nov 25;252(22):8035–8039. [PubMed] [Google Scholar]
- ELLMAN G. L. Tissue sulfhydryl groups. Arch Biochem Biophys. 1959 May;82(1):70–77. doi: 10.1016/0003-9861(59)90090-6. [DOI] [PubMed] [Google Scholar]
- Foust G. P., Mayhew S. G., Massey V. Complex formation between ferredoxin triphosphopyridine nucleotide reductase and electron transfer proteins. J Biol Chem. 1969 Feb 10;244(3):964–970. [PubMed] [Google Scholar]
- KEISTER D. L., SAN PIETRO A., STOLZENBACH F. E. Pyridine nucleotide transhydrogenase from spinach. I. Purification and properties. J Biol Chem. 1960 Oct;235:2989–2996. [PubMed] [Google Scholar]
- LOWRY O. H., ROSEBROUGH N. J., FARR A. L., RANDALL R. J. Protein measurement with the Folin phenol reagent. J Biol Chem. 1951 Nov;193(1):265–275. [PubMed] [Google Scholar]
- Sancho J., Peleato M. L., Gomez-Moreno C., Edmondson D. E. Purification and properties of ferredoxin-NADP+ oxidoreductase from the nitrogen-fixing cyanobacteria Anabaena variabilis. Arch Biochem Biophys. 1988 Jan;260(1):200–207. doi: 10.1016/0003-9861(88)90441-9. [DOI] [PubMed] [Google Scholar]
- Schneeman R., Krogmann D. W. Polycation interactions with spinach ferredoxin-nicotinamide adenine dinucleotide phosphate reductase. J Biol Chem. 1975 Jul 10;250(13):4965–4971. [PubMed] [Google Scholar]
- Vallejos R. H., Ceccarelli E., Chan R. Evidence for the existence of a thylakoid intrinsic protein that binds ferredoxin-NADP+ oxidoreductase. J Biol Chem. 1984 Jul 10;259(13):8048–8051. [PubMed] [Google Scholar]
