Reaction of cytochrome c with imidazole

Schejter, Abel; Aviram, Irit

doi:10.1021/bi00829a021

Cited by 76 publications

(50 citation statements)

References 13 publications

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“…This is in agreement with the findings of Schejter & Aviram (1969) who found a preferential binding of imidazole to the cytochrome in the Fe 3~ oxidation state of the heine iron.…”

Section: Resultssupporting

confidence: 93%

Crystallization and X-ray structure determination of cytochrome c2 from Rhodobacter sphaeroides in three crystal forms

Axelrod¹,

Fehér²,

Allen³

et al. 1994

Acta Cryst D

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Cytochrome c2 serves as the secondary electron donor that reduces the photo-oxidized bacteriochlorophyll dimer in photosynthetic bacteria. Cytochrome c2 from Rhodobacter sphaeroides has been crystallized in three different forms. At high ionic strength, crystals of a hexagonal space group (P6~22) were obtained, while at low ionic strength, triclinic (P1) and tetragonal (P4~2~2) crystals were formed. The three-dimensional structures of the cytochrome in all three crystal forms have been determined by X-ray diffraction at resolutions of 2.20 ~ (hexagonal), 1.95 A, (triclinic) and 1.53 A (tetragonal). The most significant difference observed was the binding of an imidazole molecule to the iron atom of the heme group in the hexagonal structure. This binding displaces the sulfur atom of Met l00, which forms the axial ligand in the triclinic and tetragonal structures.

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“…This is in agreement with the findings of Schejter & Aviram (1969) who found a preferential binding of imidazole to the cytochrome in the Fe 3~ oxidation state of the heine iron.…”

Section: Resultssupporting

confidence: 93%

Crystallization and X-ray structure determination of cytochrome c2 from Rhodobacter sphaeroides in three crystal forms

Axelrod¹,

Fehér²,

Allen³

et al. 1994

Acta Cryst D

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“…We observed that while 30% of cyt c 1 retained a midpoint potential comparable to the value found for highly active bc 1 complex (250 -270 mV), 70% showed a lower midpoint potential of 146 Ϯ 6 mV. It has been shown that imidazole can displace the methionine axial heme iron ligand of cyt c (27) and that this type of ligand substitution is accompanied by a decrease in the midpoint potential of the heme (28). We suggest therefore that a similar ligand substitution occurs in cyt c 1 of the bc 1 complex when imidazole is used in the purification procedure.…”

Section: Polypeptide Composition and Aggregation Statesupporting

confidence: 56%

Expression and One-Step Purification of a Fully Active Polyhistidine-Tagged Cytochromebc1Complex fromRhodobacter sphaeroides

Guergova-Kuras¹,

Salcedo‐Hernández²,

Bechmann³

et al. 1999

Protein Expression and Purification

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“…Also the spectrum of the reduction product obtained within 1 min of mixing is that of ferrocytochrome c. These observations do not, however, necessarily argue against our interpretation, since the loss of S(IV) [presumably 0-bonded as sulfite to Fe(JI)] is expected to be very rapid. Thus the rate of release of X from X-FeIIcyt c is 8.8 X 10-4 secat 250 when X = CO (14), 4.27 X 10-3 sec' at 25°when X = CN- (14), and 1.08 X 10-1 sec-1 at 21°when X = imidazole (15). As this order probably parallels the affinity of Felicyt c for X, and the affinity of Fe cyt c for oxygen-bonded Jigands is expected to be small, rapid dissociation of sulfite-Felicyt c is not surprising.…”

Section: Remote Attack Pathwaymentioning

confidence: 95%

Reduction of Ferricytochrome c by Dithionite Ion: Electron Transfer by Parallel Adjacent and Remote Pathways

Creutz

Sutin

1973

Proc. Natl. Acad. Sci. U.S.A.

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The kinetics of the reduction of horseheart ferricytochrome c by sodium dithionite (phosphate buffer-sodium chloride; pH 6.5, ; = 1.0, 250) features two reaction pathways; one with the rate constant kg = 1.17 X 104 M-l sec , the other with the rate constant klk2/k_,-6.0 X 104 M-1 sec-. These pathways are interpreted in terms of remote attack (possibly by way of the exposed edge of the porphyrin system) and adjacent attack (requiring the opening of the heme crevice). The limiting rate for the adjacent pathway (k, = 30 sec-) is in good agreement with the rate of heme-crevice opening of ferricytochrome c determined in other studies. The implication of the adjacent attack pathway to the function of cytochrome c in vivo is discussed.Cytochrome c, an electron carrier in the mitochondrial respiratory chain, is a relatively stable metalloprotein consisting of one heme group and one polypeptide chain. The heme group is covalently bonded to the protein by thioether bridges between the porphyrin ring and two cysteine residues in the peptide chain; in ferricytochrome c (Fe"i'cyt c) the heme group lies in a crevice of the essentially globular protein with an edge of the porphyrin ring located at the surface of the molecule (1). The iron atom is situated in the plane of the porphyrin ring with its fifth and sixth coordination sites occupied by a ring nitrogen atom of histidine-18 and the sulfur atom of methionine-80.Recent studies of substitution (2) and electron transfer (3) reactions of ferricytochrome c have revealed two pathways for electron transfer: an adjacent attack pathway requiring the rupture of the iron-sulfur bond or the opening of the heme crevice (with a rate constant of 60 sec at 25°), and a remote attack pathway involving an indirect route, possibly the exposed edge of the porphyrin ring system. This paper is concerned with the reaction of ferricytochrome c with the potent, frequently used reducing agent, dithionite [E' for the reduction of sulfur(IV) to dithionite is -0.46 v at pH 7 (4)]. This work extends the earlier studies (3), and shows that the mechanism of reduction of ferricytochrome c may depend upon both the nature of the reducing agent and its concentration. MATERIALS AND METHODSSolutions 5-10 /M in Sigma horse-heart Type III cytochrome c (normally used without further purification) were prepared in 0.04 M phosphate-0.91 M NaCl, having a pH of 6.5. Cytochrome c, purified in the following manner, was used in a Abbreviations: Fe"' cyt c, ferricytochrome c; Fe"l cyt c, ferrocytochrome c. * This is publication III in a series, "Mechanisms of the Reactions of Cytochrome c." The preceding paper in this series is ref. 3.t Author to whom reprint requests should be addressed. 1701 few runs. A 60-mg sample of the commercial hemeprotein was subjected to gel filtration on a 2 X 20-cm column of Sephadex G-50 (fine) in 0.04 M phosphate (pH 6.5)-0.91 M NaCl at 40. The center fraction (about 3 ml) of the filtrate was loaded onto a 4 X 20-cm column of Bio-Rex 70 (100-200 mesh, Na+ form) and eluted with a li...

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Reaction of cytochrome c with imidazole

Cited by 76 publications

References 13 publications

Crystallization and X-ray structure determination of cytochrome c2 from Rhodobacter sphaeroides in three crystal forms

Crystallization and X-ray structure determination of cytochrome c2 from Rhodobacter sphaeroides in three crystal forms

Expression and One-Step Purification of a Fully Active Polyhistidine-Tagged Cytochromebc1Complex fromRhodobacter sphaeroides

Reduction of Ferricytochrome c by Dithionite Ion: Electron Transfer by Parallel Adjacent and Remote Pathways

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