title: The crystal structures of human steroidogenic factor-1 and liver receptor homologue-1.
abstract: Steroidogenic factor-1 (SF-1) and liver receptor homologue-1 (LRH-1) belong to the fushi tarazu factor 1 subfamily of nuclear receptors. SF-1 is an essential factor for sex determination during development and regulates adrenal and gonadal steroidogenesis in the adult, whereas LRH-1 is a critical factor for development of endodermal tissues and regulates cholesterol and bile acid homeostasis. Regulatory ligands are unknown for SF-1 and LRH-1. A reported mouse LRH-1 structure revealed an empty pocket in a region commonly occupied by ligands in the structures of other nuclear receptors, and pocket-filling mutations did not alter the constitutive activity observed. Here we report the crystal structures of the putative ligand-binding domains of human SF-1 at 2.1-A resolution and human LRH-1 at 2.5-A resolution. Both structures bind a coactivator-derived peptide at the canonical activation-function surface, thus adopting the transcriptionally activating conformation. In human LRH-1, coactivator peptide binding also occurs to a second site. We discovered in both structures a phospholipid molecule bound in a pocket of the putative ligand-binding domain. MS analysis of the protein samples used for crystallization indicated that the two proteins associate with a range of phospholipids. Mutations of the pocket-lining residues reduced the transcriptional activities of SF-1 and LRH-1 in mammalian cell transfection assays without affecting their expression levels. These results suggest that human SF-1 and LRH-1 may be ligand-binding receptors, although it remains to be seen if phospholipids or possibly other molecules regulate SF-1 or LRH-1 under physiological conditions.
authors.affiliation: Plexxikon, Inc., 91 Bolivar Drive, Berkeley, CA 94710, USA.
authors.forename: Weiru
authors.initials: W
authors.lastname: Wang
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.forename: Adhirai
authors.initials: A
authors.lastname: Marimuthu
authors.forename: Heike I
authors.initials: HI
authors.lastname: Krupka
authors.forename: Maryam
authors.initials: M
authors.lastname: Tabrizizad
authors.forename: Rafe
authors.initials: R
authors.lastname: Shelloe
authors.forename: Upasana
authors.initials: U
authors.lastname: Mehra
authors.forename: Kevin
authors.initials: K
authors.lastname: Eng
authors.forename: Hoa
authors.initials: H
authors.lastname: Nguyen
authors.forename: Calvin
authors.initials: C
authors.lastname: Settachatgul
authors.forename: Ben
authors.initials: B
authors.lastname: Powell
authors.forename: Michael V
authors.initials: MV
authors.lastname: Milburn
authors.forename: Brian L
authors.initials: BL
authors.lastname: West
mesh_terms: D000595:Amino Acid Sequence; D002460:Cell Line; D003461:Crystallography; D003587:Cytomegalovirus; D004268:DNA-Binding Proteins / Q000235:genetics / Q000648:ultrastructure*; D005822:Genetic Vectors; D018398:Homeodomain Proteins; D006801:Humans; D008024:Ligands; D013058:Mass Spectrometry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000648:ultrastructure*; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000235:genetics / Q000648:ultrastructure*; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D008024:Ligands; C515057:NR5A1 protein, human; C082631:NR5A2 protein, human; D018160:Receptors, Cytoplasmic and Nuclear; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; C515058:steroidogenic factor 1, mouse