title: Evidence for ligand-independent transcriptional activation of the human estrogen-related receptor alpha (ERRalpha): crystal structure of ERRalpha ligand binding domain in complex with peroxisome proliferator-activated receptor coactivator-1alpha.
abstract: The crystal structure of the ligand binding domain (LBD) of the estrogen-related receptor alpha (ERRalpha, NR3B1) complexed with a coactivator peptide from peroxisome proliferator-activated receptor coactivator-1alpha (PGC-1alpha) reveals a transcriptionally active conformation in the absence of a ligand. This is the first x-ray structure of ERRalpha LBD, solved to a resolution of 2.5 A, and the first structure of a PGC-1alpha complex. The putative ligand binding pocket (LBP) of ERRalpha is almost completely occupied by side chains, in particular with the bulky side chain of Phe328 (corresponding to Ala272 in ERRgamma and Ala350 in estrogen receptor alpha). Therefore, a ligand of a size equivalent to more than approximately 4 carbon atoms could only bind in the LBP, if ERRalpha would undergo a major conformational change (in particular the ligand would displace H12 from its agonist position). The x-ray structure thus provides strong evidence for ligand-independent transcriptional activation by ERRalpha. The interactions of PGC-1alpha with ERRalpha also reveal for the first time the atomic details of how a coactivator peptide containing an inverted LXXLL motif (namely a LLXYL motif) binds to a LBD. In addition, we show that a PGC-1alpha peptide containing this nuclear box motif from the L3 site binds ERRalpha LBD with a higher affinity than a peptide containing a steroid receptor coactivator-1 motif and that the affinity is further enhanced when all three leucine-rich regions of PGC-1alpha are present.
authors.affiliation: Protein Structure Unit, Novartis Institutes for Biomedical Research, Basel, Switzerland. jeorge.kallen@pharma.novartis.com
authors.forename: Joerg
authors.initials: J
authors.lastname: Kallen
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Schlaeppi
authors.forename: Francis
authors.initials: F
authors.lastname: Bitsch
authors.forename: Ireos
authors.initials: I
authors.lastname: Filipuzzi
authors.forename: Alain
authors.initials: A
authors.lastname: Schilb
authors.forename: Virginie
authors.initials: V
authors.lastname: Riou
authors.forename: Alexander
authors.initials: A
authors.lastname: Graham
authors.forename: Andre
authors.initials: A
authors.lastname: Strauss
authors.forename: Martin
authors.initials: M
authors.lastname: Geiser
authors.forename: Brigitte
authors.initials: B
authors.lastname: Fournier
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D002244:Carbon / Q000737:chemistry; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004305:Dose-Response Relationship, Drug; D006360:Heat-Shock Proteins / Q000378:metabolism*; D051548:Histone Acetyltransferases; D006801:Humans; D007313:Insecta; D007930:Leucine / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D009154:Mutation; D056920:Nuclear Receptor Coactivator 1; D010455:Peptides / Q000737:chemistry; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000378:metabolism; D011960:Receptors, Estrogen / Q000737:chemistry* / Q000378:metabolism; D013696:Temperature; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D000097983:ERRalpha Estrogen-Related Receptor
chemical_list: D002244:Carbon; D006360:Heat-Shock Proteins; D051548:Histone Acetyltransferases; D007930:Leucine; D008024:Ligands; D056920:Nuclear Receptor Coactivator 1; D010455:Peptides; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D018160:Receptors, Cytoplasmic and Nuclear; D011960:Receptors, Estrogen; D014157:Transcription Factors; D000097983:ERRalpha Estrogen-Related Receptor; C486497:PPARGC1A protein, human; C538859:NCOA1 protein, human