Video Experimental Relacionado
Updated: Aug 15, 2026
11:42
Iterative Optimization of DNA Duplexes for Crystallization of SeqA-DNA Complexes
Published on: November 1, 2012
Estructura cristalina del tetramero del núcleo del lacrepresor y sus implicaciones para el bucle del ADN
A M Friedman1, T O Fischmann, T A Steitz
1Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University, New Haven, CT 06520-8114, USA.
Science (New York, N.Y.)
|June 23, 1995
Resumen
La estructura cristalina del represor lac (LacR) complejo con un inductor revela su forma tetramérica. Esta estructura explica cómo LacR se une al ADN y sugiere flexibilidad en la unión del operador.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- Biología Estructural Biología estructural.
- La bioquímica es la bioquímica.
Sus antecedentes:
- El represivo lac (LacR) controla la transcripción del operón lac en Escherichia coli.
- Comprender la estructura de LacR es crucial para descifrar los mecanismos de regulación génica.
Objetivo del estudio:
- Para determinar la estructura cristalina de alta resolución del fragmento de núcleo LacR unido a un inductor.
- Para dilucidar la estructura cuaternaria y la interfaz de unión al ADN de LacR.
Principales métodos:
- Cristalografía de rayos X con una resolución de 2.6 A.
- Análisis de la estructura del complejo proteína-ligando.
Principales resultados:
- La estructura cristalina revela un complejo LacR tetramérico formado por dos dímeros paralelos.
- Se forma una hendidura en forma de V entre los dímeros, posicionando los dominios de unión al ADN en un lado.
- El dominio de tetramerización comprende un haz de cuatro hélices.
- Las mutaciones que afectan a la unión al ADN se agrupan cerca del extremo N.
- El modelado sugiere la vinculación de operadores paralelos adyacentes y la orientación de dímeros flexibles.
Conclusiones:
- La estructura determinada proporciona información sobre el mecanismo de unión al ADN de LacR.
- La flexibilidad estructural permite a LacR acomodar espacios variados entre operadores.
- Este trabajo mejora nuestra comprensión de la regulación genética de los procariotas.
Videos de Conceptos Relacionados
02:09Operons
Prokaryotes can control gene expression through operons—DNA sequences consisting of regulatory elements and clustered, functionally related protein-coding genes. Operons use a single promoter sequence to initiate transcription of a gene cluster (i.e., a group of structural genes) into a single mRNA molecule. The terminator sequence ends transcription. An operator sequence, located between the promoter and structural genes, prohibits the operon’s transcriptional activity if bound by a repressor...
02:13Cooperative Binding of Transcription Regulators
Transcriptional regulators bind to specific cis-regulatory sequences in the DNA to regulate gene transcription. These cis-regulatory sequences are very short, usually less than ten nucleotide pairs in length. The short length means that there is a high probability of the exact same sequence randomly occurring throughout the genome. Since regulators can also bind to groups of similar sequences, this further increases the chances of random binding. Transcriptional regulators form dimers that...
02:04Co-activators and Co-repressors
Gene transcription is regulated by the synergistic action of several proteins that form a complex at a gene regulatory site. This is observed in eukaryotes, where the regulation of gene expression is a complex process. Regulatory proteins in eukaryotes can broadly be classified into two types – regulators that bind directly to specific DNA sequences and co-regulators that associate with regulatory proteins but cannot directly bind to the DNA. These co-regulators are further divided into...
02:13Cooperative Binding of Transcription Regulators
Transcriptional regulators bind to specific cis-regulatory sequences in the DNA to regulate gene transcription. These cis-regulatory sequences are very short, usually less than ten nucleotide pairs in length. The short length means that there is a high probability of the exact same sequence randomly occurring throughout the genome. Since regulators can also bind to groups of similar sequences, this further increases the chances of random binding. Transcriptional regulators form dimers that...
02:04Co-activators and Co-repressors
Gene transcription is regulated by the synergistic action of several proteins that form a complex at a gene regulatory site. This is observed in eukaryotes, where the regulation of gene expression is a complex process. Regulatory proteins in eukaryotes can broadly be classified into two types – regulators that bind directly to specific DNA sequences and co-regulators that associate with regulatory proteins but cannot directly bind to the DNA. These co-regulators are further divided into...
01:25Inducible Operons: lac Operon
The lac operon in Escherichia coli is a model for understanding inducible gene regulation and metabolic flexibility. It integrates local control by lactose and global regulation through catabolite repression, enabling E. coli to preferentially metabolize glucose when available and switch to lactose utilization when glucose is scarce.Structure and Function of the lac OperonThe lac operon contains three structural genes: lacZ (β-galactosidase), lacY (lactose permease), and lacA (thiogalactoside...