Respiratory enzymes of Thiobacillus ferrooxidans. A kinetic study of electron transfer between iron and rusticyanin in sulfate media.

Blake, Robert C.; Shute, Elizabeth A.

doi:10.1016/s0021-9258(18)48126-4

Cited by 55 publications

(25 citation statements)

References 36 publications

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“…Kinetic measurements at a single wavelength were performed on the stopped-flow spectrophotometer described previously (Blake & Shute, 1987). The reactants to be rapidly mixed were prepared in identical solutions of acidic anionic media and added to separate syringes of the stopped-flow spectrophotometer.…”

mentioning

confidence: 99%

Respiratory Enzymes of Thiobacillus ferrooxidans. Kinetic Properties of an Acid-Stable Iron:Rusticyanin Oxidoreductase

Blake¹,

Shute²

1994

Biochemistry

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Rusticyanin is an acid-stable, soluble blue copper protein found in abundance in the periplasmic space of Thiobacillus ferrooxidans, an acidophilic bacterium capable of growing autotrophically on soluble ferrous sulfate. An acid-stable iron:rusticyanin oxidoreductase activity was partially purified from cell-free extracts of T. ferrooxidans. The enzyme-catalyzed, iron-dependent reduction of the rusticyanin exhibited three kinetic properties characteristic of aerobic iron oxidation by whole cells. (i) A survey of 14 different anions indicated that catalysis by the oxidoreductase occurred only in the presence of sulfate or selenate, an anion specificity identical to that of whole cells. (ii) Saturation with both sulfatoiron(II) and the catalyst produced a concentration-independent rate constant of 3 s-1 for the reduction of the rusticyanin, which is an electron transfer reaction sufficiently rapid to account for the flux of electrons through the iron respiratory chain. (iii) Values for the enzyme-catalyzed pseudo-first-order rate constants for the reduction of the rusticyanin showed a hyperbolic dependence on the concentration of sulfatoiron(II) with a half-maximal effect at 300 microM, a value similar to the apparent KM for iron shown by whole cells. On the basis of these favorable comparisons between the behavior patterns of isolated biomolecules and those of whole cells, this iron:rusticyanin oxidoreductase is postulated to be the primary cellular oxidant of ferrous ions in the iron respiratory electron transport chain of T. ferrooxidans.

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mentioning

confidence: 99%

Respiratory Enzymes of Thiobacillus ferrooxidans. Kinetic Properties of an Acid-Stable Iron:Rusticyanin Oxidoreductase

Blake¹,

Shute²

1994

Biochemistry

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“…That potential represents an extrapolated value in the absence of anions that might bind preferentially to soluble iron in either oxidation state. The sulfate anions (SO 4 2– , HSO 4 1– ) that were present in our solutions at pH 1.5 bind more tightly to the ferric ion than they do to the ferrous ion ( Blake and Shute, 1987 ). Consequently, one would expect the reduction potential for the ferric/ferrous couple to be slightly lower than 770 mV in sulfuric acid at pH 1.5, which is precisely what we observed.…”

Section: Resultsmentioning

confidence: 88%

Ferrimicrobium acidiphilum Exchanges Electrons With a Platinum Electrode via a Cytochrome With Reduced Absorbance Maxima at 448 and 605 nm

et al. 2021

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Ferrimicrobium acidiphilum is a Gram-positive member of the Actinobacteria phylum that can respire aerobically or anaerobically with soluble Fe(II) or Fe(III), respectively, in sulfuric acid at pH 1.5. Cyclic voltammetry measurements using intact F. acidiphilum at pH 1.5 produced fully reversible voltammograms that were highly reproducible. The maximum current observed with the anodic peak was considerably less than was the maximum current observed with the cathodic peak. This difference was attributed to the competition between the platinum electrode and the soluble oxygen for the available electrons that were introduced by the cathodic wave into this facultative aerobic organism. The standard reduction potential of the intact organism was determined to be 786 mV vs. the standard hydrogen electrode, slightly more positive than that of 735 mV that was determined for soluble iron at pH 1.5 using the same apparatus. Chronocoulometry measurements conducted at different cell densities revealed that the intact organism remained in close proximity to the working electrode during the measurement, whereas soluble ionic iron did not. When the cyclic voltammetry of intact F. acidiphilum was monitored using an integrating cavity absorption meter, the only small changes in absorbance that were detected were consistent with the participation of a cellular cytochrome with reduced absorbance peaks at 448 and 605 nm. The cytochrome that participated in the exchange of electrons between the intact organism and extracellular solid electrodes like platinum was the same cytochrome whose oxidation was previously shown to be rate-limiting when the organism respired aerobically on extracellular soluble iron.

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“…Absorbance spectra were obtained on a Cary 14 dual-beam spectrophotometer as described earlier (Blake and Shute, 1987). The alkaline pyridine hemochromogen spectra of cytochrome 579 were obtained as described elsewhere (Bartsch, 1971).…”

Section: Spectral and Kinetic Characterization Of Purified Cytochrome 579mentioning

confidence: 99%

“…The alkaline pyridine hemochromogen spectra of cytochrome 579 were obtained as described elsewhere (Bartsch, 1971). Kinetic measurements were performed on an RSM-1000™ stopped flow spectrophotometer equipped with a rapid-scan module that permitted the collection and analysis of absorbance data as a function of both time and wavelength (Blake and Shute, 1987). The samples of cytochrome 579 and ferrous or ferric ions were prepared in identical solutions of sulfuric acid, pH 1.5, and added to separate syringes of the stopped flow spectrophotometer.…”

Section: Spectral and Kinetic Characterization Of Purified Cytochrome 579mentioning

confidence: 99%

“…Inset, the dependence of the logarithm (Continued) in the reaction, in this case, one. If the data in Figures 6A,B were simply linear second-order plots, then the resulting logarithm of the ratio of rate constants would be single value that one could use to calculate a single value of ΔE 0 Cyt579 from the calculated value of ΔE 0 Fe = 680 mV in 0.02 M sulfuric acid, pH 1.5 (Blake and Shute, 1987;Blake et al, 1991). However, the striking nonlinearity of the kinetic data in Figures 6A,B creates the relationship shown in Figure 6C, where the logarithm of the ratio of kinetic rate constants is itself a linear function of the logarithm of the concentration of soluble iron.…”

Section: Electron Transfer Reactions Between Cytochrome 579 and Soluble Ironmentioning

confidence: 99%

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Homogeneous Cytochrome 579 Is an Octamer That Reacts Too Slowly With Soluble Iron to Be the Initial Iron Oxidase in the Respiratory Chain of Leptospirillum ferriphilum

et al. 2021

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The exact role that cytochrome 579 plays in the aerobic iron respiratory chain of Leptospirillum ferriphilum is unclear. This paper presents genomic, structural, and kinetic data on the cytochrome 579 purified from cell-free extracts of L. ferriphilum cultured on soluble iron. Electrospray mass spectrometry of electrophoretically homogeneous cytochrome 579 yielded two principal peaks at 16,015 and 16,141 Daltons. N-terminal amino acid sequencing of the purified protein yielded data that were used to determine the following: there are seven homologs of cytochrome 579; each homolog possesses the CXXCH heme-binding motif found in c-type cytochromes; each of the seven sequenced strains of L. ferriphilum expresses only two of the seven homologs of the cytochrome; and each homolog contains an N-terminal signal peptide that directs the mature protein to an extra-cytoplasmic location. Static light scattering and macroion mobility measurements on native cytochrome 579 yielded masses of 125 and 135 kDaltons, respectively. The reduced alkaline pyridine hemochromogen spectrum of the purified cytochrome had an alpha absorbance maximum at 567 nm, a property not exhibited by any known heme group. The iron-dependent reduction and oxidation of the octameric cytochrome exhibited positively cooperative kinetic behavior with apparent Hill coefficients of 5.0 and 3.7, respectively, when the purified protein was mixed with mM concentrations of soluble iron. Consequently, the extrapolated rates of reduction at sub-mM iron concentrations were far too slow for cytochrome 579 to be the initial iron oxidase in the aerobic respiratory chain of L. ferriphilum. Rather, these observations support the hypothesis that the acid-stable cytochrome 579 is a periplasmic conduit of electrons from initial iron oxidation in the outer membrane of this Gram-negative bacterium to a terminal oxidase in the plasma membrane.

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Respiratory enzymes of Thiobacillus ferrooxidans. A kinetic study of electron transfer between iron and rusticyanin in sulfate media.

Cited by 55 publications

References 36 publications

Respiratory Enzymes of Thiobacillus ferrooxidans. Kinetic Properties of an Acid-Stable Iron:Rusticyanin Oxidoreductase

Respiratory Enzymes of Thiobacillus ferrooxidans. Kinetic Properties of an Acid-Stable Iron:Rusticyanin Oxidoreductase

Ferrimicrobium acidiphilum Exchanges Electrons With a Platinum Electrode via a Cytochrome With Reduced Absorbance Maxima at 448 and 605 nm

Homogeneous Cytochrome 579 Is an Octamer That Reacts Too Slowly With Soluble Iron to Be the Initial Iron Oxidase in the Respiratory Chain of Leptospirillum ferriphilum

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