title: Does azurin bind to the transactivation domain of p53? A Trp phosphorescence study.
abstract: The bacterial redox protein azurin has been shown to be able to enter into cancer cells and induce apoptosis by stabilizing p53. Although the formation of a complex between the two proteins has been demonstrated, little is known about their binding features. We investigated the interaction between the transcription activation domain of p53 (p53(1-63)) and Pseudomonas aeruginosa azurin using fluorescence and phosphorescence spectroscopic techniques. Trp phosphorescence lifetime measurements revealed conformational changes in azurin induced by the interaction with p53(1-63). Acrylamide quenching of Trp phosphorescence also indicated a significant increase in the overall flexibility of azurin upon binding to p53(1-63). We show that azurin binds to the N-terminal region of p53 with a dissociation constant in the 5-10 μM range. No change in the fluorescence and phosphorescence emission of p53(1-63) was detected in the presence of azurin. This result indicated that no Trp residue of p53(1-63) is located in the interaction site with azurin and therefore suggested that the azurin binding site does not overlap that of MDM2, the protein that plays a crucial role in the p53 regulation. The present results may assist in the design of novel cancer treatments based on p53 stabilization by azurin.
authors: Istituto di Biofisica, Consiglio Nazionale delle Ricerche, via G. Moruzzi, 1, 56124 Pisa, Italy. edi.gabellieri@pi.ibf.cnr.it
authors: Edi
authors: E
authors: Gabellieri
authors: Monica
authors: M
authors: Bucciantini
authors: Massimo
authors: M
authors: Stefani
authors: Patrizia
authors: P
authors: Cioni
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D001400:Azurin / Q000737:chemistry / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000494:pharmacology*; D001665:Binding Sites; D006801:Humans; D008163:Luminescent Measurements; D008958:Models, Molecular; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051736:Proto-Oncogene Proteins c-mdm2 / Q000737:chemistry; D011550:Pseudomonas aeruginosa / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D001426:Bacterial Proteins; D016159:Tumor Suppressor Protein p53; D001400:Azurin; D014364:Tryptophan; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2