The low temperature magnetic circular dichroism spectra of iron-sulphur proteins II. Two-iron ferredoxins

Thomson, Andrew J.; Cammack, Richard; Hall, D.O.; Rao, K. K.; Briat, B.; Rivoal, J. C.; Badoz, J.

doi:10.1016/0005-2795(77)90266-5

Cited by 27 publications

(18 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The absorption spectrum (Fig. 5) appears similar to those of ferredoxins containing [4Fe-451 + clusters but not [2Fe-2S]l+ or [2Fe-2S]2+ clusters (Stephens et al, 1978;Thomson et al, 1977). E.p.r.…”

Section: Main Fractionmentioning

confidence: 65%

Purification and characterization of the inactive MoFe protein (NifB-Kp1) of the nitrogenase from nifB mutants of Klebsiella pneumoniae

Hawkes¹,

Smith²

1983

Biochemical Journal

View full text Add to dashboard Cite

The inactive MoFe protein of nitrogenase, NifB-Kp1, from two distinct nifB mutants of Klebsiella pneumoniae, Kp5058 (a nifB point mutant) and UNF1718 (a nifB, nifJ double mutant) has been purified and characterized. NifB-Kp1 can be activated by reaction with the iron-molybdenum cofactor, FeMoco, extracted from active MoFe protein. NifB-Kp1 purified from either source had similar properties and was contaminated with an approximately equimolar amount of protein of mol.wt. 21 000. Like active wild-type Kp1, it was an alpha 2 beta 2 tetramer, but it was far less stable than Kp1, deteriorating rapidly at temperatures above 8 degrees C or on mild oxidation. NifB-Kp1 preparations contained 0.4-0.9 Mo and 9.0 +/- 0.9 Fe atoms . mol-1 and, when activated by FeMoco, had a specific activity of approx. 500 units . mg-1. The Mo in our preparations was not associated with the e.p.r. signal normally observed from FeMoco. All preparations exhibited a weak gav. = 1.95 e.p.r. signal which was probably not associated with activatable protein.

show abstract

Section: Main Fractionmentioning

confidence: 65%

Purification and characterization of the inactive MoFe protein (NifB-Kp1) of the nitrogenase from nifB mutants of Klebsiella pneumoniae

Hawkes¹,

Smith²

1983

Biochemical Journal

View full text Add to dashboard Cite

show abstract

“…The low-temperature absorption spectrum of the oxidized [2Fe-2S] ferredoxin from Spirulina maxima is similar, having maxima at approx. 420 and 470 nm (Thomson et al, 1977). i: Fig.…”

Section: Resultsmentioning

confidence: 97%

Detection by low-temperature magnetic circular-dichroism spectroscopy of optical absorption bands due to molybdenum (V) in the form of xanthine oxidase giving the Desulpho Inhibited e.p.r. signal

Peterson¹,

Godfrey²,

Thomson³

et al. 1986

Biochemical Journal

View full text Add to dashboard Cite

The magnetic circular-dichroism (m.c.d.) spectra in the temperature range 1.5-100 K and the electronic absorption spectra at 4.2 and 295 K were measured for a number of desulpho xanthine oxidase derivatives. There were no significant differences between the absorption spectra that could be attributed to molybdenum. However, the visible-region m.c.d. spectrum of the ethanediol-treated metalloprotein (which gives rise to the Desulpho Inhibited e.p.r. signal) contained features assignable to Mo(V) absorption-bands. This is the first report of the detection of optical bands of Mo(V) in an enzyme in the presence of other chromophoric centres.

show abstract

“…25,26 Moreover, VHVT MCD saturation magnetization data at discrete wavelengths showed that all the observed MCD bands originate from [Fe 2 S 2 ] + clusters with S = 1/2 ground states and provided no evidence for contributions from the valence-delocalized S = 9/2 [Fe 2 S 2 ] + clusters that were observed by EPR. Parallel EPR studies indicated the addition of 50% (v/v) ethylene glycol to obtain a frozen glass for VTMCD studies results in complete loss of the EPR signals associated with the S = 9/2 [Fe 2 S 2 ] + clusters.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic and Redox Studies of Valence-Delocalized [Fe₂S₂]⁺ Centers in Thioredoxin-like Ferredoxins

et al. 2015

View full text Add to dashboard Cite

Reduced forms of the C56S and C60S variants of the thioredoxin-like Clostridium pasteurianum [Fe2S2] ferredoxin (CpFd) provide the only known examples of valence-delocalized [Fe2S2]+ clusters, which constitute a fundamental building block of all higher nuclearity Fe-S clusters. In this work, we have revisited earlier work on the CpFd variants and carried out redox and spectroscopic studies on the [Fe2S2]2+,+ centers in wild-type and equivalent variants of the highly homologous and structurally characterized Aquifex aeolicus ferredoxin 4 (AaeFd4) using EPR, UV-visible-NIR absorption, CD and variable-temperature MCD, and protein-film electrochemistry. The results indicate that the [Fe2S2]+ centers in the equivalent AaeFd4 and CpFd variants reversibly interconvert between similar valence-localized S = 1/2 and valence-delocalized S = 9/2 forms as a function of pH, with pKa values in the range 8.3-9.0, due to protonation of the coordinated serinate residue. However, freezing high-pH samples results in partial or full conversion from valence-delocalized S = 9/2 to valence-localized S = 1/2 [Fe2S2]+ clusters. MCD saturation magnetization data for valence-delocalized S = 9/2 [Fe2S2]+ centers facilitated determination of transition polarizations and thereby assignments of low-energy MCD bands associated with the Fe−Fe interaction. The assignments provide experimental assessment of the double exchange parameter, B, for valence-delocalized [Fe2S2]+ centers and demonstrate that variable-temperature MCD spectroscopy provides a means of detecting and investigating the properties of valence-delocalized S = 9/2 [Fe2S2]+ fragments in higher nuclearity Fe-S clusters. The origin of valence delocalization in thioredoxin-like ferredoxin Cys-to-Ser variants and Fe-S clusters in general is discussed in light of these results.

show abstract

The low temperature magnetic circular dichroism spectra of iron-sulphur proteins II. Two-iron ferredoxins

Cited by 27 publications

References 10 publications

Purification and characterization of the inactive MoFe protein (NifB-Kp1) of the nitrogenase from nifB mutants of Klebsiella pneumoniae

Purification and characterization of the inactive MoFe protein (NifB-Kp1) of the nitrogenase from nifB mutants of Klebsiella pneumoniae

Detection by low-temperature magnetic circular-dichroism spectroscopy of optical absorption bands due to molybdenum (V) in the form of xanthine oxidase giving the Desulpho Inhibited e.p.r. signal

Spectroscopic and Redox Studies of Valence-Delocalized [Fe₂S₂]⁺ Centers in Thioredoxin-like Ferredoxins

Contact Info

Product

Resources

About

The low temperature magnetic circular dichroism spectra of iron-sulphur proteins II. Two-iron ferredoxins

Cited by 27 publications

References 10 publications

Purification and characterization of the inactive MoFe protein (NifB-Kp1) of the nitrogenase from nifB mutants of Klebsiella pneumoniae

Purification and characterization of the inactive MoFe protein (NifB-Kp1) of the nitrogenase from nifB mutants of Klebsiella pneumoniae

Detection by low-temperature magnetic circular-dichroism spectroscopy of optical absorption bands due to molybdenum (V) in the form of xanthine oxidase giving the Desulpho Inhibited e.p.r. signal

Spectroscopic and Redox Studies of Valence-Delocalized [Fe2S2]+ Centers in Thioredoxin-like Ferredoxins

Contact Info

Product

Resources

About

Spectroscopic and Redox Studies of Valence-Delocalized [Fe₂S₂]⁺ Centers in Thioredoxin-like Ferredoxins