title: Tyrosine phosphorylation turns alkaline transition into a biologically relevant process and makes human cytochrome c behave as an anti-apoptotic switch.
abstract: Cytochrome c (Cc) is a key protein in cell life (respiration) and cell death (apoptosis). On the one hand, it serves as a mitochondrial redox carrier, transferring electrons between the membrane-embedded complexes III and IV. On the other hand, it acts as a cytoplasmic apoptosis-triggering agent, forming the apoptosome with apoptosis protease-activating factor-1 (Apaf-1) and activating the caspase cascade. The two functions of cytochrome c are finely tuned by the phosphorylation of tyrosines and, in particular, those located at positions 48 and 97. However, the specific cytochrome c-phosphorylating kinase is still unknown. To study the structural and functional changes induced by tyrosine phosphorylation in cytochrome c, we studied the two phosphomimetic mutants Y48E and Y97E, in which each tyrosine residue is replaced by glutamate. Such substitutions alter both the physicochemical features and the function of each mutant compared with the native protein. Y97E is significantly less stable than the WT species, whereas Y48E not only exhibits lower values for the alkaline transition pK                         (a) and the midpoint redox potential, but it also impairs Apaf-1-mediated caspase activation. Altogether, these findings suggest that the specific phosphorylation of Tyr48 makes cytochrome c act as an anti-apoptotic switch.
authors.affiliation: Instituto de Bioquímica Vegetal y Fotosíntesis, cicCartuja, Universidad de Sevilla-CSIC, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: García-Heredia
authors.forename: Antonio
authors.initials: A
authors.lastname: Díaz-Quintana
authors.forename: Maria
authors.initials: M
authors.lastname: Salzano
authors.forename: Mar
authors.initials: M
authors.lastname: Orzáez
authors.forename: Enrique
authors.initials: E
authors.lastname: Pérez-Payá
authors.forename: Miguel
authors.initials: M
authors.lastname: Teixeira
authors.forename: Miguel A
authors.initials: MA
authors.lastname: De la Rosa
authors.forename: Irene
authors.initials: I
authors.lastname: Díaz-Moreno
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017209:Apoptosis; D053477:Apoptotic Protease-Activating Factor 1 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D003198:Computer Simulation; D045304:Cytochromes c / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation; D011485:Protein Binding / Q000235:genetics; D011487:Protein Conformation; D055550:Protein Stability; D014443:Tyrosine / Q000737:chemistry / Q000235:genetics*
chemical_list: D053477:Apoptotic Protease-Activating Factor 1; D014443:Tyrosine; D045304:Cytochromes c; D053453:Caspase 9