Biomaterial Database

Purification and properties of a flavodoxin from the heterocystous cyanobacterium Anabaena sphaerica. 1993

A F Yakunin, and P C Hallenbeck, and Troshina OYu, and I N Gogotov

Institute of Soil Science and Photosynthesis, Pushchino, Moscow region, Russia.

A flavodoxin was purified to homogeneity from the nitrogen-fixing heterocystous cyanobacterium Anabaena sphaerica grown under iron-limited conditions. The protein has a molecular mass of 21 kDa, and its spectral properties and amino-acid composition are very close to that of flavodoxins from other cyanobacteria. A. sphaerica flavodoxin supported the activities of A. sphaerica NADP reductase and Clostridium butyricum hydrogenase in reconstituted systems with illuminated plant chloroplasts as reductant. With the use of polyclonal anti-flavodoxin antiserum it was found that nitrogen-fixing cultures of A. sphaerica grown under iron-sufficient conditions contain low but significant amounts of flavodoxin (0.2-0.6 micrograms/mg crude extract protein) which increased dramatically (to 8-15 micrograms/mg crude extract protein) after the iron concentration in the medium was decreased to below 1 microM Fe. The flavodoxin content of both iron-limited and iron-sufficient. A. sphaerica was also shown to depend upon the growth phase of the (batch) cultures with a maximum at early exponential phase, coinciding with maximal in-vivo nitrogenase activity. These results suggest that A. sphaerica flavodoxin not only substitutes for ferredoxin under iron-limiting conditions, but also fulfills some specific role under iron-sufficient conditions.

UI	MeSH Term	Description	Entries
D009586	Nitrogen Fixation	The process in certain BACTERIA; FUNGI; and CYANOBACTERIA converting free atmospheric NITROGEN to biologically usable forms of nitrogen, such as AMMONIA; NITRATES; and amino compounds.	Diazotrophy,Diazotrophic Activity,Dinitrogen Fixation,N2 Fixation,Activities, Diazotrophic,Activity, Diazotrophic,Diazotrophic Activities,Fixation, Dinitrogen,Fixation, N2,Fixation, Nitrogen
D004579	Electron Transport	The process by which ELECTRONS are transported from a reduced substrate to molecular OXYGEN. (From Bennington, Saunders Dictionary and Encyclopedia of Laboratory Medicine and Technology, 1984, p270)	Respiratory Chain,Chain, Respiratory,Chains, Respiratory,Respiratory Chains,Transport, Electron
D005287	Ferredoxin-NADP Reductase	An enzyme that catalyzes the oxidation and reduction of FERREDOXIN or ADRENODOXIN in the presence of NADP. EC 1.18.1.2 was formerly listed as EC 1.6.7.1 and EC 1.6.99.4.	Adrenodoxin Reductase,Iron-Sulfur Protein Reductase,NADPH-Ferredoxin Reductase,Ferredoxin NADP Reductase,Iron Sulfur Protein Reductase,NADPH Ferredoxin Reductase,Protein Reductase, Iron-Sulfur,Reductase, Adrenodoxin,Reductase, Ferredoxin-NADP,Reductase, Iron-Sulfur Protein,Reductase, NADPH-Ferredoxin
D005418	Flavodoxin	A low-molecular-weight (16,000) iron-free flavoprotein containing one molecule of flavin mononucleotide (FMN) and isolated from bacteria grown on an iron-deficient medium. It can replace ferredoxin in all the electron-transfer functions in which the latter is known to serve in bacterial cells.
D000596	Amino Acids	Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.	Amino Acid,Acid, Amino,Acids, Amino
D017033	Anabaena	A genus of CYANOBACTERIA consisting of trichomes that are untapered with conspicuous constrictions at cross-walls. A firm individual sheath is absent, but a soft covering is often present. Many species are known worldwide as major components of freshwater PLANKTON and also of many saline lakes. The species DOLICHOSPERMUM FLOS-AQUAE is responsible for acute poisonings of various animals.