Isolation and characterization of two different flavodoxins from the eukaryote Chlorella fusca

• Published in: Biochemical journal Vol. 302; no. 3; pp. 807 - 811
• Main Authors: Peleato, M.L, Ayora, S, Inda, L.A, Gomez-Moreno, C
• Format: Journal Article
• Language: English
• Published: Colchester Portland Press 15-09-1994
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Blotting, Western; Chlorella; Chlorella - chemistry; Chlorella - metabolism; Chromatography, High Pressure Liquid; flavin mononucleotide; Flavodoxin - chemistry; Flavodoxin - isolation & purification; Flavodoxin - metabolism; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; iron; Isoelectric Point; Miscellaneous; Molecular Sequence Data; Molecular Weight; NADP - metabolism; nutrient deficiencies; Oxidation-Reduction; Proteins; purification; redox potential; redox proteins; redox reactions; Spectrophotometry, Ultraviolet; Chemical reduction; Molecular form; Purification; Algae; Chlorella fusca; Chlorophycophyta; Flavodoxin; Flavoprotein; Biological activity; Aminoacid sequence; Thallophyta
• DOI: 10.1042/bj3020807
• EISSN: 1470-8728
• ISSN: 0264-6021

Two different molecular forms of flavodoxin from the green alga Chlorella fusca have been purified to homogeneity and their properties compared. The molecular masses are 22 kDa (flavodoxin I) and 20 kDa (flavodoxin II). Western blots of axenic crude extract show the two bands. Both are single polypeptide chains and their N-terminal sequences differ but are very similar. Each form contains 1 mol of FMN/mol of apoprotein, exhibits a typical flavodoxin u.v.-visible absorption spectrum and does not contain covalently bound phosphate. The oxidation-reduction properties of the FMN in the flavodoxins differ considerably. Redox potentials of flavodoxin I at pH 8 are -240 mV for the oxidized/semiquinone couple and -350 mV for the semiquinone/hydroquinone couple. Flavodoxin II gives more electronegative values: -278 mV and -458 mV respectively. Flavodoxin II fulfils better the redox requirements for photosynthetic electron transport and, as expected, it is more efficient at mediating NADP+ photoreduction in the photosynthetic electron flow. A new h.p.l.c. method for flavodoxin purification is described, which is useful for the isolation of very similar anionic proteins.