Tryptophan Corepressor
Tryptophan Corepressor - Related Videos
12:07
Chemical Modification of the Tryptophan Residue in a Recombinant Ca2+-ATPase N-domain for Studying Tryptophan-ANS FRET
0 Views •
2021
ANS binds to the Ca2+-ATPase recombinant N-domain. Fluorescence spectra display a FRET-like pattern upon excitation at a wavelength of 295 nm. NBS-mediated chemical modification of Trp quenches the fluorescence of the N-domain, which leads to the absence of energy transfer (FRET) between the Trp residue and ANS.
![Radiosynthesis of 1-(2-[<sup>18</sup>F]Fluoroethyl)-L-Tryptophan using a One-pot, Two-step Protocol](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F63025.jpg%3Fv%3D2026-09-01%252022%253A39%253A53&w=750&q=75)
08:33
Radiosynthesis of 1-(2-[18F]Fluoroethyl)-L-Tryptophan using a One-pot, Two-step Protocol
0 Views •
Cited by 4 •
2021
Here, we describe the radiosynthesis of 1-(2-[18F]Fluoroethyl)-L-tryptophan, a positron emission tomography imaging agent for studying tryptophan metabolism, using a one-pot, two-step strategy in a radiochemistry synthesis system with good radiochemical yields, high enantiomeric excess, and high reliability.
09:31
PCR Mutagenesis, Cloning, Expression, Fast Protein Purification Protocols and Crystallization of the Wild Type and Mutant Forms of Tryptophan Synthase
0 Views •
Cited by 2 •
2020
This article presents a series of consecutive methods for the expression and purification of Salmonella typhimurium tryptophan synthase comp this protocol a rapid system to purify the protein complex in a day. Covered methods are site-directed mutagenesis, protein expression in Escherichia coli, affinity chromatography, gel filtration chromatography, and crystallization.
02:42
Transcription Attenuation in Prokaryotes
0 Views •
2020
Transcriptional attenuation occurs when RNA transcription is prematurely terminated due to the formation of a terminator mRNA hairpin structure. Bacteria use these hairpins to regulate the transcription process and control the synthesis of several amino acids including histidine, lysine, threonine, and phenylalanine. Transcription attenuation takes place in the non-coding regions of mRNA. There are several different mechanisms used to attenuate transcription. In ribosome mediated...
01:58
Prokaryotic Transcriptional Activators and Repressors
0 Views •
2020
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...
FAQs
The key molecular event is an allosteric change in the trp repressor. After tryptophan binds, the protein adopts a conformation that can recognize the trp operon's operator. This association interferes with RNA polymerase and blocks transcription. The mechanism therefore converts the concentration of a metabolic product into a direct signal controlling expression of genes needed for its biosynthesis.
Abundant tryptophan signals that the cell already has access to the amino acid, so continued synthesis of biosynthetic enzymes becomes unnecessary. Corepressor-dependent repression reduces transcription of the trp operon, which conserves cellular energy and materials. This feedback arrangement couples metabolic sufficiency to reduced gene expression rather than allowing biosynthesis to continue unchecked.
The small-molecule corepressor and the repressor protein have different jobs. The corepressor binds the protein, whereas the activated repressor binds the operator. This separation allows a metabolite, rather than the DNA-binding protein alone, to control transcriptional repression. It also demonstrates allosteric regulation, in which ligand binding changes the protein's ability to interact with DNA.
A focused analysis can compare gene regulation under conditions with abundant tryptophan and conditions with lower availability. Researchers can examine whether the repressor associates with the operator, whether RNA polymerase is blocked, and whether production of tryptophan-biosynthesis enzymes is reduced. These linked observations connect metabolite availability with transcriptional output and test feedback regulation.
In Escherichia coli, the trp operon provides a clear biological context because its genes encode enzymes for tryptophan biosynthesis. The system illustrates how bacteria coordinate a biosynthetic pathway through transcriptional control. When the amino acid is sufficient, repression limits pathway-enzyme expression, connecting cellular metabolism with resource conservation rather than treating each gene as an isolated unit.
A result consistent with corepressor-mediated repression is a coordinated decrease in trp-operon transcription and biosynthetic-enzyme production when tryptophan is abundant. The molecular explanation should include repressor binding at the operator and interference with RNA polymerase, not merely a change in enzyme abundance. This interpretation identifies transcriptional feedback as the link between metabolite availability and pathway control.