Abstract
Abstract Flavodoxin has been crystallized from Peptostreptococcus elsdenii grown at low iron concentrations. The properties of this protein are similar to those of flavodoxin from Clostridium pasteurianum. It has a molecular weight of about 15,000 and contains 1 molecule of flavin mononucleotide per molecule of protein. It does not contain labile sulfide or iron. It lacks the amino acid histidine. Ferredoxin and flavodoxin are interchangeable in the oxidation of pyruvate by extracts of P. elsdenii from media either high or low in iron, and in the phosphoroclastic reaction of C. pasteurianum. On a molar basis flavodoxin is somewhat less effective than ferredoxin in these systems. Flavodoxin is reduced by light irradiation in the presence of EDTA and an intermediate having a spectrum characteristic of flavin neutral semiquinone is generated. The rate and extent of reduction are pH-dependent. The spectrum of the semiquinone is unaffected at high pH and by high concentrations of urea. The extinction coefficient of oxidized flavodoxin at 445 mµ is 10,200 m-1 cm-1. The extinction coefficient of flavodoxin semiquinone at 580 mµ is 4,500 m-1 cm-1.
Highlights
Flavodoxin was found in cells grown on low iron medium. it was not detected in extracts from cells obtained from either the medium containing yeast extract plus iron, or the medium containing corn steep liquor [5]
Cells grown on low iron medium contained almost 1% (w/w) flavodoxin; ferredoxin but not flavodoxin was isolated from cells grown in high iron medium
The properties of the flavoprotein isolated from P. elsdenii closely resemble those of flavodoxin from C. pasteurianum (I, 2)
Summary
METHODS AND MATERIALSGrowth of &licroorganisms and Preparation of Crude ExtractsP. elsclenii, strain LC 1 [6] was maintained as described by Walker [5]. Cultures of 40 liters in 12-gallon bottles were grown according to Walker [5], except that corn steep liquor was replaced by yeast extract, and lactic acid neutralized with sodium hydroxide was used in place of commercial sodium lactate. The medium with a low content of iron contained 0.4% (w/v) Difco yeast extract adjusted to pH 7.4 with NaOH, 1.4rr/, (w/v) sodium lactate, and 0.0270 (w/v) sodium dithionite. Medium with a high iron content contained in addition 0.004% (w/v) FeS04.7 H,O. The dried cells were ground to a fine powder and stored at -20” [5]. Cell yields from the yeast extract media were similar to those obtained previously with corn steep liquor (0.75 to 1.0 g, dry weight, per liter of medium)
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