Complexes of iron and cobalt tetrasulfonated phthalocyanines with apocytochrome c

Przywarska-Boniecka, Helena; Ostropolska, Lucja

doi:10.1016/s0162-0134(00)80106-3

Cited by 11 publications

(2 citation statements)

References 25 publications

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“…However, the existence of a noncovalent interaction between heme and apocytochrome c is consistent with the results of Przywarska-Boniecka and Ostropolska (1982), who reported that apocytochrome c binds tetrasulfonated pthalocyanines, inducing changes in the conformation of apocytochrome c similar to those that we observed. Upon prolonged incubation of the pthalocyanine-apocytochrome c complex with a molar excess of heme, the bound pthalocyanine was replaced by heme (Przywarska-Boniecka & Ostropolska, 1982). Formation of a stable noncovalent complex between heme and apocytochrome c is also consistent with evidence from X-ray structures of holocytochromes c that there are extensive interactions between heme and various amino acid residues in widely distributed regions of the protein (Bushnell et Wavelength (nm)…”

Section: Discussionsupporting

confidence: 93%

“…The detection of a noncovalent interaction between heme and apocytochrome c that persists in the presence of high concentrations of cyanide appears to contradict a previous report that failed to find any such interaction (Parr & Taniuchi, 1980). However, the existence of a noncovalent interaction between heme and apocytochrome c is consistent with the results of Przywarska-Boniecka and Ostropolska (1982), who reported that apocytochrome c binds tetrasulfonated pthalocyanines, inducing changes in the conformation of apocytochrome c similar to those that we observed. Upon prolonged incubation of the pthalocyanine-apocytochrome c complex with a molar excess of heme, the bound pthalocyanine was replaced by heme (Przywarska-Boniecka & Ostropolska, 1982).…”

Section: Discussioncontrasting

confidence: 57%

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Noncovalent Binding of Heme Induces a Compact Apocytochrome c Structure

Dumont

Corin²,

Campbell³

1994

Biochemistry

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Mitochondrial holocytochrome c contains heme that is covalently attached to the protein in a reaction catalyzed by the enzyme cytochrome c heme lyase. In the absence of heme, apocytochrome c, the precursor to holocytochrome c, is unfolded. We find that purified apocytochrome c binds noncovalently to heme. Binding is accompanied by changes in the optical absorption spectrum of heme and by quenching of the tryptophan fluorescence of the protein. The affinity of apocytochrome c for heme, as well as the stoichiometry of binding, appears to depend on whether or not cyanide is present and on the oxidation state of heme. Under reducing conditions, in the presence of cyanide, the association appears to be 1:1, with a binding constant of about 10(7) M-1. Under oxidized conditions, there may be multiple hemes bound per molecule of apocytochrome c. Upon binding to heme, apocytochrome c exhibits a mobility similar to that of holocytochrome c in gel filtration chromatography and velocity gradient ultracentrifugation, indicating that the heme-protein complex adopts a structure that is almost as compact as that of holocytochrome c. Changes in the circular dichroism spectrum of apocytochrome c are consistent with an increase in the alpha-helical content of the protein on binding heme. The compact structure of the noncovalent heme-apocytochrome c complex may represent an intermediate in the de novo folding of cytochrome c.

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Section: Discussionsupporting

confidence: 93%