RESUMEN

Among nuclear receptors, the androgen receptor (AR) is unique in that its ligand-binding domain (LBD) interacts with the FXXLF motif in the N-terminal domain, resembling coactivator LXXLL motifs. We compared AR- and estrogen receptor alpha-LBD interactions of the wild-type AR FXXLF motif and coactivator transcriptional intermediary factor 2 LXXLL motifs and variants of these motifs. Random mutagenesis revealed a key role for the F residues in FXXLF motifs in high-affinity and selective AR LBD interaction. The FXXLF motif in full-length AR and transcriptional intermediary factor 2 LXXLL motifs competed for an overlapping binding site. A computer model of the AR LBD/AR FXXLF complex showed that the bulky F residues are buried in a deep coactivator-binding groove. The corresponding groove in estrogen receptor alpha LBD is considerably shallower, explaining lack of binding of any of the FXXLF motifs tested. FXXLF and LXXLL motif interaction depended on different charged amino acid residues in the AR LBD present at opposite ends of the coactivator groove. In conclusion, our data demonstrate the importance of a deep hydrophobic groove and alternative usage of charged amino acids in specifying peptide binding to the AR LBD.

Asunto(s)

Receptores Androgénicos/química , Receptores Androgénicos/metabolismo , Factores de Transcripción/química , Secuencias de Aminoácidos/genética , Secuencia de Aminoácidos , Sustitución de Aminoácidos/genética , Sitios de Unión , Unión Competitiva , Análisis Mutacional de ADN , Receptor alfa de Estrógeno/química , Receptor alfa de Estrógeno/genética , Receptor alfa de Estrógeno/metabolismo , Humanos , Ligandos , Modelos Moleculares , Datos de Secuencia Molecular , Coactivador 2 del Receptor Nuclear , Péptidos/química , Conformación Proteica , Receptores Androgénicos/genética , Factores de Transcripción/metabolismo , Técnicas del Sistema de Dos Híbridos