RESUMO
Computational models reveal the structural origins of cooperativity in the association of the DNA binding domains (DBD) of p53 (and its two homologues p63 and p73) with consensus DNA. In agreement with experiments they show that cooperativity, as defined by sequential binding of monomers to DNA is strong for p53 and weak for homologues p63 and p73. Computations also suggest that cooperativity can arise from the dimerization of the DBD prior to binding the DNA for all 3 family members. Dimerization between the DBDs is driven by packing interactions originating in residues of helix H1 and loop L3, while DNA binding itself is dominated by local and global electrostatics. Calculations further suggest that low affinity oligomerization of the p53 DBD can precede the oligomerization of the tetramerization domain (TD). During synthesis of multiple chains on the polysome, this may increase fidelity by reducing the possibility of the highly hydrophobic TD from nonspecific aggregation. Mutations have been suggested to test these findings.
Assuntos
Biologia Computacional , Proteínas de Ligação a DNA/química , Proteínas Nucleares/química , Fosfoproteínas/química , Multimerização Proteica , Proteína Supressora de Tumor p53/química , Proteínas Supressoras de Tumor/química , Sequência de Aminoácidos , DNA/metabolismo , Proteínas de Ligação a DNA/metabolismo , Dados de Sequência Molecular , Proteínas Mutantes/química , Proteínas Mutantes/metabolismo , Proteínas Nucleares/metabolismo , Fosfoproteínas/metabolismo , Ligação Proteica , Estrutura Quaternária de Proteína , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Alinhamento de Sequência , Propriedades de Superfície , Termodinâmica , Proteína Tumoral p73 , Proteína Supressora de Tumor p53/metabolismo , Proteínas Supressoras de Tumor/metabolismoRESUMO
Florescence anisotropy measurements using FAM-labelled p53 peptides showed that the binding of the peptides to MDM2 was dependant upon the phosphorylation of p53 at Thr18 and that this binding was modulated by the electrostatic properties of MDM2. In agreement with computational predictions, the binding to phosphorylated p53 peptide, in comparison to the unphosphorylated p53 peptide, was enhanced upon mutation of 3 key residues on the MDM2 surface.