Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 2 de 2
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Mol Endocrinol ; 23(1): 25-34, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18988706

RESUMO

Despite the fact that many nuclear receptors are ligand dependent, the existence of obligate regulatory ligands is debated for some receptors, including steroidogenic factor 1 (SF-1). Although fortuitously bound bacterial phospholipids were discovered in the structures of the SF-1 ligand-binding domain (LBD), these lipids might serve merely as structural ligands. Thus, we examined whether exogenously added phospholipids would exchange for these bacterial lipids and bind to SF-1. Here, we report the first crystal structure of the SF-1 LBD bound by the exchanged phosphatidylcholine. Although the bound phosphatidylcholine phospholipid mimics the conformation of bound bacterial phosphoplipids, two surface loops, L2-3 and L11-12, surrounding the entrance to the pocket vary significantly between different SF-1 LBD structures. Based on this observation, we hypothesized that a bound ligand might control the conformations of loops L2-3 and L11-12, and that conserved residues in these dynamic loops could influence ligand binding and the receptor function. Consistent with this hypothesis, impaired phospholipid exchange and diminished transcriptional activity were observed for loop L11-12 SF-1 mutants and for the loop L2-3 human mutant R255L. The endocrine disease associated with this L2-3 mutation coupled with our cellular and biochemical data suggest that critical residues at the mouth of the ligand-binding pocket have evolved for efficient binding of phospholipid ligands and for achieving optimal SF-1 activity.


Assuntos
Fosfolipídeos/metabolismo , Fator Esteroidogênico 1/química , Fator Esteroidogênico 1/metabolismo , Sequência de Aminoácidos , Substituição de Aminoácidos , Animais , Sequência de Bases , Sítios de Ligação , Sequência Conservada , Cristalografia por Raios X , Primers do DNA/genética , Evolução Molecular , Humanos , Técnicas In Vitro , Lecitinas/química , Lecitinas/metabolismo , Ligantes , Camundongos , Modelos Moleculares , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Fosfolipídeos/química , Conformação Proteica , Estrutura Terciária de Proteína , Homologia de Sequência de Aminoácidos , Fator Esteroidogênico 1/genética
2.
Mol Cell Biol ; 28(24): 7476-86, 2008 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-18838537

RESUMO

SUMO modification of nuclear receptors, including the constitutively active receptor steroidogenic factor 1 (SF-1; NR5A1), is proposed to repress their transcriptional activity. We examined the functional and structural consequences of SF-1 sumoylation at two conserved lysines (Lys119 and Lys194) that reside adjacent to the DNA-binding domain (DBD) and ligand-binding domain (LBD), respectively. Surprisingly, while previous loss-of-function studies predicted that sumoylation at Lys194 would greatly impact SF-1 function, the conformation and coregulator recruitment of fully sumoylated SF-1 LBD protein was either unchanged or modestly impaired. Sumoylation at Lys194 also modestly reduced Ser203 phosphorylation. In contrast to these findings, sumoylation of the DBD at Lys119 resulted in a marked and selective loss of DNA binding to noncanonical SF-1 targets, such as inhibinalpha; this binding deficit was extended to all sites when the sumoylated human mutant (R92Q) protein, which exhibits lower activity, was used. Consistent with this result, the K119R mutant, compared to wild-type SF-1, was selectively recruited to a "SUMO-sensitive" site in the endogenous inhibinalpha promoter, leading to increased transcription. DNA binding and sumoylation of Lys119 appeared to be mutually exclusive, suggesting that once SF-1 is bound to DNA, sumoylation may be less important in regulating SF-1 activity. We propose that sumoylation of nuclear receptors imposes an active posttranslational mark that dampens recognition of SUMO-sensitive target genes to restrain their expression.


Assuntos
Regulação da Expressão Gênica , Processamento de Proteína Pós-Traducional , Proteínas Modificadoras Pequenas Relacionadas à Ubiquitina/metabolismo , Fator Esteroidogênico 1/metabolismo , Sequência de Aminoácidos , Animais , Linhagem Celular , DNA/metabolismo , Humanos , Inibinas/genética , Inibinas/metabolismo , Lisina/metabolismo , Camundongos , Modelos Moleculares , Dados de Sequência Molecular , Regiões Promotoras Genéticas , Conformação Proteica , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Proteínas Modificadoras Pequenas Relacionadas à Ubiquitina/genética , Fator Esteroidogênico 1/genética , Transcrição Gênica
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...