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Related Concept Videos

Co-activators and Co-repressors02:04

Co-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...
Co-activators and Co-repressors02:04

Co-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...
RNA Polymerase II Accessory Proteins02:36

RNA Polymerase II Accessory Proteins

Proteins that regulate transcription can do so either via direct contact with RNA Polymerase or through indirect interactions facilitated by adaptors, mediators, histone-modifying proteins, and nucleosome remodelers. Direct interactions to activate transcription is seen in bacteria as well as in some eukaryotic genes. In these cases, upstream activation sequences are adjacent to the promoters, and the activator proteins interact directly with the transcriptional machinery. For example, in...
Eukaryotic Transcription Inhibitors01:52

Eukaryotic Transcription Inhibitors

Certain biochemical processes, such as embryonic development and cell growth regulation, depend on the repression of specific genes. DNA binding proteins known as eukaryotic transcription inhibitors regulate the repression of gene expression in eukaryotes. The presence of these inhibitors at the required location and time in the cell is triggered by the presence of hormones and additional signals from other cells.
Eukaryotic transcription inhibitors usually contain two distinct domains, a DNA...
Repressible Operon: trp Operon01:21

Repressible Operon: trp Operon

The trp operon in Escherichia coli exemplifies a repressible operon. It regulates the synthesis of tryptophan through repressor-mediated transcriptional control and attenuation. This dual regulatory mechanism ensures tryptophan biosynthesis occurs only when needed, conserving cellular resources.Structure of the trp OperonThe trp operon consists of five structural genes (trpE, trpD, trpC, trpB, and trpA) that encode enzymes for tryptophan biosynthesis. These genes are transcribed as a single...
Prokaryotic Transcriptional Activators and Repressors01:58

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...

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Related Experiment Video

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In vivo Application of the REMOTE-control System for the Manipulation of Endogenous Gene Expression
08:54

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Published on: March 29, 2019

Reducing lambda repressor to the core.

Maxim B Prigozhin1, Krishnarjun Sarkar, Dennis Law

  • 1Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA.

The Journal of Physical Chemistry. B
|February 16, 2011
PubMed
Summary

Researchers identified a minimal protein core, λ(blue1), from the lambda repressor fragment. This two-helix bundle protein folds as fast as the original fragment, revealing key insights into protein folding dynamics.

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Area of Science:

  • Protein folding dynamics
  • Biophysics
  • Structural biology

Background:

  • Lambda repressor fragment λ(*)(6-85) is a known fast-folding small protein.
  • Understanding minimal protein folding cores is crucial for protein design and function studies.

Purpose of the Study:

  • To identify and characterize the smallest possible folding core of the lambda repressor fragment λ(*)(6-85).
  • To investigate the thermodynamic and kinetic properties of reduced protein structures.

Main Methods:

  • Molecular dynamics simulations to predict stable reduced structures.
  • Experimental validation using circular dichroism, fluorescence spectroscopy, and temperature jump relaxation spectroscopy.
  • Thermal melt analysis to determine peptide stability.

Main Results:

  • Identified two energetically stable reduced structures, with the most stable being a two-helix bundle (λ(blue1)).
  • λ(blue1) exhibits cooperative folding, matching the melting temperature and folding rate of the full-length λ(*)(6-85).
  • Experimental results align with theoretical predictions regarding peptide stability.

Conclusions:

  • The two-helix bundle λ(blue1) represents a minimal, cooperatively folding protein core.
  • This finding provides significant insights into the fundamental principles of protein folding and stability.
  • The study demonstrates the successful reduction of a protein fragment to its essential folding unit.