Redox properties of cytochrome c.
ABSTRACT The redox properties of cytochromes (cyt) c, a ubiquitous class of heme-containing electron transport proteins, have been extensively investigated over the last two decades. The reduction potential (E degrees') is central to the chemistry of cyt c for two main reasons. First, E degrees' influences both the thermodynamic and kinetic aspects of the electron exchange reaction with redox partners. Second, this thermodynamic parameter is remarkably sensitive to changes in the properties of the heme and the protein matrix, and hence can be profitably used for the investigation of the solution chemistry of cyt c. This research area owes much to the exploitation of voltammetric techniques for the determination of E degrees' for metalloproteins, which dates back to the late 1970s. Since then, much effort has been devoted to the comprehension of the molecular factors that control E degrees' in cyt c, which include first coordination sphere effects on the heme iron, the interactions of the heme group with the surrounding polypeptide chain and the solvent, and also include medium effects related to the nature and ionic composition of the solvent, pH, the presence of potential protein ligands, and the temperature. This article provides an overview of the most significant advances made in this field recently.
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ABSTRACT: The crystal structure of a 1:1 complex between yeast cytochrome c peroxidase and yeast iso-1-cytochrome c was determined at 2.3 A resolution. This structure reveals a possible electron transfer pathway unlike any previously proposed for this extensively studied redox pair. The shortest straight line between the two hemes closely follows the peroxidase backbone chain of residues Ala194, Ala193, Gly192, and finally Trp191, the indole ring of which is perpendicular to, and in van der Waals contact with, the peroxidase heme. The crystal structure at 2.8 A of a complex between yeast cytochrome c peroxidase and horse heart cytochrome c was also determined. Although crystals of the two complexes (one with cytochrome c from yeast and the other with cytochrome c from horse) grew under very different conditions and belong to different space groups, the two complex structures are closely similar, suggesting that cytochrome c interacts with its redox partners in a highly specific manner.Science 01/1993; 258(5089):1748-55. · 31.03 Impact Factor
Article: Ion binding to cytochrome c.[show abstract] [hide abstract]
ABSTRACT: This paper is a further study of ion binding to protein surfaces and builds on the studies of the binding of [Cr(CN)6]3- and [Fe(edta)(H2O)]- previously reported [Williams et al. (1982) FEBS Lett. 15, 293-299; Eley et al. (1982) Eur. J. Biochem. 124, 295-303]. In the present paper the binding of polyaminocarboxylate complexes of gadolinium have been studied. Eight ion-binding sites have been identified on the surface of cytochrome c. These exhibit different binding specificities which, in some cases, are not full understood. However it is clear that simple outer-sphere interactions are not the sole determining factor for the association of metal ion complexes with proteins. The NMR paramagnetic difference spectrum method has been shown to be good at locating binding sites and revealing qualitative differences in their relative affinities for a range of complex types. However the use of relaxation probes is not a good method for the quantitative determination of binding constants; for this, isostructural shift probes must be sought.European Journal of Biochemistry 06/1988; 173(3):607-15. · 3.58 Impact Factor
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ABSTRACT: In cytochrome c, ligation of the heme iron by the methionine-80 sulfur plays a major role in determining the structure and the thermodynamic stability of the protein. In the ferric state, this bond is reversibly broken by moderately acid or alkaline pH's (pK's 2.5 and 9.4, respectively) and by exogenous ligands. NMR studies of horse ferricytochrome c in which the Met-65 and Met-80 methyl groups were chemically enriched with 13C demonstrate that, at 59 degrees C, a temperature at which the protein is still folded, the sulfur-iron bond is already partially broken. This structural change corresponds to the reversible disappearance upon moderate heating of the 695 nm band, characteristic of the sulfur-iron coordination of this protein. The thermal effect results from a shift in the alkaline pK from 9.4 at 25 degrees C to 8.2 at 59 degrees C. The exchange rate from iron-bound to free methionine-80 at 59 degrees C is 1.8 s-1, as measured by saturation transfer experiments. The free and bound methionine-80 epsilon-methyl groups in the 1H spectrum are assigned as (1.87, 2.25) and -21.43, respectively; in the 13C spectrum they are assigned as 15.6 and 12.8, respectively (all these values are in ppm from 3-(trimethylsilyl)propionic-2,2,3,3-d4 acid, sodium salt).Biochemistry 11/1995; 34(43):14209-12. · 3.38 Impact Factor