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Prokaryotic Transcriptional Activators and Repressors

Prokaryotic Transcriptional Activators and Repressors

The organization of prokaryotic genes in their genome is notably different from that of eukaryotes. Prokaryotic genes are organized, such that the genes for proteins involved in the same biochemical process or function are located together in groups. This group of genes, along with their regulatory elements, are collectively known as an operon. The functional genes in an operon are transcribed together to give a single strand of mRNA known as polycistronic mRNA.
Transcription of prokaryotic...

Prokaryotic Transcriptional Activators and Repressors

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The organization of prokaryotic genes in their genome is notably different from that of eukaryotes. Prokaryotic genes are organized, such that the genes for proteins involved in the same biochemical process or function are located together in groups. This group of genes, along with their regulatory elements, are collectively known as an operon. The functional genes in an operon are transcribed together to give a single strand of mRNA known as polycistronic mRNA.
Transcription of prokaryotic...

Operon Model

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The operon model represents a fundamental mechanism of gene regulation in prokaryotes, enabling coordinated expression of genes involved in related metabolic or functional pathways. Operons consist of structural genes, a promoter, and an operator, with transcription regulated by repressors, activators, and small effector molecules.Structure and Function of OperonsAn operon is a cluster of structural genes transcribed together under the control of a single promoter. The promoter region...

Cooperative Binding of Transcription Regulators

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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...

Inducible Operons: lac Operon

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Restriction enzymes are bacterial enzymes used to cut DNA in a sequence-specific manner. To cleave DNA, they bind to specific palindromic sequences called restriction sites. Such palindromic DNA sequences or inverted repeats are commonly found in regions of functional significance, such as the origin of replication, gene operator sites, and regions containing transcription termination signals.
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Related Experiment Video

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In Vitro Directed Evolution of a Restriction Endonuclease with More Stringent Specificity

In Vitro Directed Evolution of a Restriction Endonuclease with More Stringent Specificity

Published on: March 25, 2020

Structural origins for selectivity and specificity in an engineered bacterial repressor-inducer pair.

Michael A Klieber¹, Oliver Scholz, Susanne Lochner

¹Department of Biology, Lehrstuhl für Biotechnik, Friedrich-Alexander University, Erlangen-Nuremberg, Germany.

The FEBS Journal

|August 29, 2009

Summary

Engineered tetracycline repressor (TetR) variants enable selective gene expression control. Structural analysis reveals specific mutations conferring selectivity for 4-ddma-atc over tetracycline.

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Area of Science:

Molecular Biology
Structural Biology
Biochemistry

Background:

The bacterial tetracycline transcription regulation system (TetR) is a key tool for studying gene expression.
Existing TetR systems lack selectivity for multiple gene expression studies.
A triple mutant TetR(K(64)L(135)I(138)) was engineered for selective induction by 4-ddma-atc.

Purpose of the Study:

To elucidate the structural basis of selective tetracycline repressor (TetR) recognition of 4-ddma-atc.
To understand the molecular mechanisms underlying TetR mutant specificity.

Main Methods:

X-ray crystallography was employed to determine the structure of TetR(K(64)L(135)I(138)) unbound and bound to 4-ddma-atc.
Structures were solved at 2.1 Å resolution.
Comparative analysis with existing TetR-ligand complex structures.

Main Results:

The crystal structures reveal conserved ligand-binding sites across different TetR variants.
Selective binding of 4-ddma-atc is attributed to specific mutations: His64-->Lys introduces hydrogen-bonding constraints.
Leu135 and Ile138 substitutions contribute via hydrophobic effects and reduced electrostatic repulsion.

Conclusions:

The engineered TetR triple mutant achieves selective gene induction through fine-tuned molecular interactions.
Structural insights provide a basis for designing novel tetracycline-based gene regulation systems.
Understanding TetR-ligand interactions is crucial for advanced synthetic biology applications.