The key role played by charge in the interaction of cytochrome c with cardiolipin.
Cytochrome c undergoes structural variations upon binding of cardiolipin, one of the phospholipids constituting the mitochondrial membrane. Although several mechanisms governing cytochrome c/cardiolipin (cyt c/CL) recognition have been proposed, the interpretation of the process remains, at least in part, unknown. To better define the steps characterizing the cyt c-CL interaction, the role of Lys72 and Lys73, two residues thought to be important in the protein/lipid binding interaction, were recently investigated by mutagenesis. The substitution of the two (positively charged) Lys residues with Asn revealed that such mutations cancel the CL-dependent peroxidase activity of cyt c; furthermore, CL does not interact with the Lys72Asn mutant. In the present paper, we extend our study to the Lys → Arg mutants to investigate the influence exerted by the charge possessed by the residues located at positions 72 and 73 on the cyt c/CL interaction. On the basis of the present work a number of overall conclusions can be drawn: (i) position 72 must be occupied by a positively charged residue to assure cyt c/CL recognition; (ii) the Arg residues located at positions 72 and 73 permit cyt c to react with CL; (iii) the replacement of Lys72 with Arg weakens the second (low-affinity) binding transition; (iv) the Lys73Arg mutation strongly increases the peroxidase activity of the CL-bound protein.
Department of Experimental Medicine and Surgery, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy.
Federica
F
Sinibaldi
Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019, Sesto Fiorentino (Fi), Italy.
Lisa
L
Milazzo
Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019, Sesto Fiorentino (Fi), Italy.
Barry D
BD
Howes
Department of Experimental Medicine and Surgery, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy.
Maria Cristina
MC
Piro
Department of Clinical Sciences and Translational Medicine, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy.
Laura
L
Fiorucci
Department of Sciences, Roma Tre University, Viale Marconi 446, 00146, Rome, Italy.|National Institute of Nuclear Physics, 'Roma Tre' Section, Via della Vasca Navale 84, 00146, Rome, Italy.
Fabio
F
Polticelli
Interdepartmental Laboratory for Electron Microscopy, Roma Tre University, Via della Vasca Navale 79, 00146, Rome, Italy.
Paolo
P
Ascenzi
Department of Clinical Sciences and Translational Medicine, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy.
Massimo
M
Coletta
Department of Chemistry "Ugo Schiff", University of Florence, Via della Lastruccia 3-13, 50019, Sesto Fiorentino (Fi), Italy. giulietta.smulevich@unifi.it.
Giulietta
G
Smulevich
Department of Clinical Sciences and Translational Medicine, University of Rome 'Tor Vergata', Via Montpellier 1, 00133, Rome, Italy. santucci@med.uniroma2.it.
Roberto
R
Santucci
D000818:Animals; D002308:Cardiolipins / Q000378:metabolism*; D045304:Cytochromes c / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004795:Enzyme Stability; D006736:Horses; D006863:Hydrogen-Ion Concentration; D008081:Liposomes / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D009195:Peroxidase / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation
D002308:Cardiolipins; D008081:Liposomes; D045304:Cytochromes c; D009195:Peroxidase
Apoptosis; Cardiolipin-cytochrome c complex; Circular dichroism; Resonance Raman