scholarly journals Short Communications. A comparative study of some kinetic and spectral properties of guanidinated and native cytochrome c

1975 ◽  
Vol 147 (1) ◽  
pp. 175-177 ◽  
Author(s):  
T Brittain ◽  
C Greenwood
Keyword(s):  
Cytochrome C ◽  
Comparative Study ◽  
Spectral Properties ◽  
Visible Spectrum ◽  
Kinetic Properties ◽  
Chemically Modified ◽  
Effects Of Ph ◽  
Kinetics Of ◽  
Kinetics Of Reduction

An investigation of the spectral and some kinetic properties of a chemically modified cytochrome c is presented. The kinetics of reduction by chromous ion and ascorbate are shown to be unchanged from that of the native molecule, as are the kinetics of NO binding. The effects of pH on the visible spectrum are discussed in terms of a possible change in the pattern of co-ordination of the molecule with changing pH.

scholarly journals Physicochemical properties of two atypical cytochromes c, Crithidia cytochrome c-557 and Euglena cytochrome c-558

1975 ◽  
Vol 149 (1) ◽  
pp. 155-167 ◽  
Author(s):  
G W Pettigrew ◽  
I Aviram ◽  
A Schejter
Keyword(s):  
Cytochrome C ◽  
Physicochemical Properties ◽  
High Spin ◽  
Visible Spectrum ◽  
Prosthetic Group ◽  
Ph Values ◽  
Cytochromes C ◽  
Kinetics Of ◽  
Alkaline Isomerization ◽  
Mitochondrial Cytochromes

Cytochrome c-557 from Crithidia oncopelti and cytochrome c-558 from Euglena gracilis are mitochondrial cytochromes c that have an atypical haem-binding site. It was of interest to know whether the loss of one thioether bond affected the physicochemical properties of these cytochromes. The thermodynamic parameters of the redox potential were measured. The reaction with imidazole, the kinetics and thermodynamics of the alkaline isomerization and the effect of heating on the visible spectrum are described for the ferricytochromes. The kinetics of the loss of cyanide, the spectral changes occurring on reduction with dithionite at alkaline pH values and the reactivity with CO are described for the ferrocytochromes. In many respects the cytochromes of the two protozoans are very similar to the cytochromes of horse and yeast. The ferricytochromes do, however, undergo a reversible transition to high-spin species on heating, which may be due to the more flexible attachment of the prosthetic group. Similarly the alkaline isomers of cytochromes c-557 and c-558 give rise to high-spin proteins above pH 11. The alkaline isomerization of cytochrome c-558, involves a pKobs. of 10 and kinetics which do not obey the model of Davis et al. [(1974) J. Biol. Chem.249, 2624-2632] for horse cytochrome c. It is proposed that a model involving two ionizations, followed by a conformation change, may fit the data. Both cytochromes c-557 and c-558 combine slowly with CO at neutral pH values.

scholarly journals The reduction of carboxymethyl-cytochrome c by chromous ions

1974 ◽  
Vol 141 (2) ◽  
pp. 455-461 ◽  
Author(s):  
Thomas Brittain ◽  
Michael T. Wilson ◽  
Colin Greenwood
Keyword(s):  
Cytochrome C ◽  
Difference Spectrum ◽  
Order Rate Constant ◽  
Stopped Flow ◽  
Methionine Residue ◽  
Ferricytochrome C ◽  
A Charge ◽  
Kinetics Of ◽  
Dependent Processes ◽  
Kinetics Of Reduction

The reduction of ferricytochrome c and ferricytochrome c carboxymethylated at the haem-linked methionine (residue 80) by Cr2+ ions was studied by stopped-flow techniques. At pH6.2 the kinetics of reduction of ferricytochrome c are simple and correspond to a second-order rate constant of 1.21×103m-1·s-1. Under identical conditions the kinetics of reduction of the carboxymethyl derivative, carboxymethyl-cytochrome c, are complex; two Cr2+-concentration-dependent processes (1.5×104m-1·s-1 and 1.3×103m-1·s-1) lead to the formation of an intermediate which decays in monomolecular fashion (0.15s-1) to form the normal fully reduced material. The kinetic difference spectrum for the overall process corresponds to that found statically, whereas the kinetic difference spectrum of the intermediate minus the oxidized form resembles that of the low-spin ferrous form of carboxymethyl-cytochrome c minus oxidized carboxymethyl-cytochrome c. A model is proposed in which the reduction of low-spin ferric carboxymethyl-cytochrome c to high-spin ferrous carboxymethyl-cytochrome c involves a low-spin ferrous intermediate. The monomolecular step involving the decay of this low-spin ferrous intermediate is associated with an activation energy of approx. 126kJ·mol-1 and is thought to involve both a change of spin state and a protein-conformational event. Although carboxymethyl-cytochrome c represents a mixture of species separable on a charge basis, the above observations were independent of which species was chosen for study.

scholarly journals Multiwavelength analysis of the kinetics of reduction of cytochrome aa3 by cytochrome c

1993 ◽  
Vol 65 (3) ◽  
pp. 1307-1317 ◽  
Author(s):  
R.W. Hendler ◽  
S.K. Bose ◽  
R.I. Shrager
Keyword(s):  
Cytochrome C ◽  
Cytochrome Aa3 ◽  
Kinetics Of ◽  
Kinetics Of Reduction

scholarly journals Kinetic studies on the reduction of cytochrome c. Reaction with dihydroxy conjugated compounds (catechols and quinols)

1982 ◽  
Vol 201 (3) ◽  
pp. 433-444 ◽  
Author(s):  
M M M Saleem ◽  
M T Wilson
Keyword(s):  
Cytochrome C ◽  
Kinetic Studies ◽  
Ring Structure ◽  
Conjugated Compounds ◽  
Electron Donation ◽  
Influence Of Ph ◽  
Kinetics Of ◽  
Related Compounds ◽  
Kinetics Of Reduction ◽  
Aromatic Ring Structure

The kinetics of reduction of cytochrome c by catechol(s), quinol(s) and related compounds were investigated by stopped-flow spectrophotometry. Studies on the influence of pH on the rates indicate that only deprotonated forms of these compounds act as reducing agents, with the dianionic forms being the most effective. The pH-independent second-order rate constants are reported. Hammett treatment of the effects of substituents on the aromatic ring structure of the reductants show that for electron transfer to occur the charge on the deprotonated species must not be withdrawn on to the substituents. Possible sites for electron donation to cytochrome c are discussed, and the results indicate that the haem edge is a likely candidate.

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