Modification of the structural and redox properties of cytochrome c by heteropolytungstate binding.
Biochim Biophys Acta
; 916(3): 402-10, 1987 Dec 18.
Article
em En
| MEDLINE
| ID: mdl-2825793
ABSTRACT
Complex formation between horse heart ferricytochrome c and large three-dimensional polyanions has been investigated, in order to study the influence of surface electrostatic interactions on the structural and redox properties of cytochrome c. Cytochrome c binds the large heteropolytungstates (NaSb9W21O86)18- and (KAs4W40O140)27- with a 1/1 polyanion/cytochrome c ratio, and the smaller ion (SiW11O39)8- with a 2/1 ratio. Upon complexation, cytochrome c undergoes structural changes that are dependent on the size and charge of the polyanion, and on the pH and ionic strength of the medium. Three different forms of complexed cytochrome c have been characterized by optical and EPR spectroscopies, in the pH range 6.5-8 an N form, close to the native structure, an A form, analogous to cytochrome c in acidic medium, and a novel B form in which the heme pocket is open but the iron remains low-spin. The redox potential of cytochrome c is lowered to 250-220 mV (vs. NHE) in the N form, and to 80 mV in the B form.
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Base de dados:
MEDLINE
Assunto principal:
Tungstênio
/
Compostos de Tungstênio
/
Grupo dos Citocromos c
/
Antimônio
Idioma:
En
Ano de publicação:
1987
Tipo de documento:
Article