title: Selective cytochrome c displacement by phosphate and Ca(2+) in brain mitochondria.
abstract: In brain mitochondria, phosphate- and Ca(2+)-dependent cytocrome c (cyt c) release reveals pools that interact differently with the inner membrane. Detachment of the phosphate-dependent pool did not influence the pool released by Ca(2+). Cyt c pools were also detected in a system of cyt c reconstituted in cardiolipin (CL) liposomes. Gradual binding of cyt c (1 nmol) to CL/2-[12-(7-nitrobenz- 2-oxa-1,3-diazol-4-yl)amino]dodecanoyl-1-hexadecan oyl-sn-glycero-3-phosphocholine (NBDC(12)-HPC) liposomes (10 nmol) produced NBD fluorescence quenching up to 0.4 nmol of added protein. Additional bound cyt c did not produce quenching, suggesting that cyt c-CL interactions originate distinct cyt c pools. Cyt c was removed from CL/NBDC(12)-HPC liposomes by either phosphate or Ca(2+), but only Ca(2+) produced fluorescence dequenching and leakage of encapsulated 8-aminonaphthalene-1,3,6-trisulfonic acid/p-xylene-bis-pyridinium bromide. In mitochondria, complex IV activity and mitochondrial membrane potential (Deltapsi(m)) were not affected by the release of the phosphate-dependent cyt c pool. Conversely, removal of cyt c by Ca(2+) caused inhibition of complex IV activity and impairment of Deltapsi(m). In a reconstituted system of mitochondria, nuclei and supernatant, cyt c detached from the inner membrane was released outside mitochondria and triggered events leading to DNA fragmentation. These events were prevented by enriching mitochondria with exogenous CL or by sequestering released cyt c with anti-cyt c antibody.
authors.affiliation: Laboratory of Biochemistry, Department of Internal Medicine, University of Perugia, Via del Giochetto, 06122, Perugia, Italy.
authors.forename: Morena
authors.initials: M
authors.lastname: Buratta
authors.forename: Lucia
authors.initials: L
authors.lastname: Piccotti
authors.forename: Silvia
authors.initials: S
authors.lastname: Giannini
authors.forename: Paolo
authors.initials: P
authors.lastname: Gresele
authors.forename: Rita
authors.initials: R
authors.lastname: Roberti
authors.forename: Lanfranco
authors.initials: L
authors.lastname: Corazzi
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002308:Cardiolipins / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism*; D053938:DNA Fragmentation; D003576:Electron Transport Complex IV / Q000378:metabolism; D066298:In Vitro Techniques; D008081:Liposomes; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D051381:Rats
chemical_list: D002308:Cardiolipins; D008081:Liposomes; D010710:Phosphates; D045304:Cytochromes c; D003576:Electron Transport Complex IV; D002118:Calcium