Cytochrome c is transformed from anti- to pro-oxidant when interacting with truncated oncoprotein prothymosin alpha.
Many apoptotic signals are known to induce release to cytosol of cytochrome c, a small mitochondrial protein with positively charged amino acid residues dominating over negatively charged ones. On the other hand, in this group, it was shown that prothymosin alpha (PT), a small nuclear protein where 53 of 109 amino acid residues are negatively charged, is truncated to form a protein of 99 amino acid residues which accumulates in cytosol during apoptosis [FEBS Lett. 467 (2000) 150]. It was suggested that positively charged cytochrome c and negatively charged truncated prothymosin alpha (tPT), when meeting in cytosol, can interact with each other. In this paper, such an interaction is shown. (1) Formation of cytochrome cz.ccirf;tPT complex is demonstrated by a blot-overlay assay. (2) Analytical centrifugation of solution containing cytochrome c and tPT reveals formation of complexes of molecular masses higher than those of these proteins. The masses increase when the cytochrome c/tPT ratio increases. High concentration of KCl prevents the complex formation. (3) In the complexes formed, cytochrome c becomes autoxidizable; its reduction by superoxide or ascorbate as well as its operation as electron carrier between the outer and inner mitochondrial membranes appear to be inhibited. (4) tPT inhibits cytochrome c oxidation by H(2)O(2), catalyzed by peroxidase. Thus, tPT abolishes all antioxidant functions of cytochrome c which, in the presence of tPT, becomes in fact a pro-oxidant. A possible role of tPT in the development of reactive oxygen species- and cytochrome c-mediated apoptosis is discussed.
Markova
Olga V
OV
Belozersky Institute of Physico-Chemical Biology, Moscow State University, Khokhlova str. 4, 119992 Moscow, Russia.
Evstafieva
Alexandra G
AG
Mansurova
Svetlana E
SE
Moussine
Sergey S
SS
Palamarchuk
Larisa A
LA
Pereverzev
Mikhail O
MO
Vartapetian
Andrey B
AB
Skulachev
Vladimir P
VP
D000818:Animals; D053148:Caspase 3; D020169:Caspases; D003574:Cytochrome c Group / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D006861:Hydrogen Peroxide; D008930:Mitochondria, Liver / Q000378:metabolism; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000037:antagonists & inhibitors; D011099:Polyglutamic Acid; D011498:Protein Precursors / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D051381:Rats; D013481:Superoxides; D013947:Thymosin / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D015032:Zinc
D003574:Cytochrome c Group; D011498:Protein Precursors; C040782:prothymosin alpha; D013481:Superoxides; D011099:Polyglutamic Acid; D013947:Thymosin; D006861:Hydrogen Peroxide; D009195:Peroxidase; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D015032:Zinc