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Allosteric Proteins-ATCase01:19

Allosteric Proteins-ATCase

Binding sites linkages can regulate a protein's function.  For example, enzyme activity is often regulated through a feedback mechanism where the end product of the biochemical process serves as an inhibitor.
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to  N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis pathway,...
Riboswitches01:56

Riboswitches

Riboswitches are non-coding mRNA domains that regulate the transcription and translation of downstream genes without the help of proteins. Riboswitches bind directly to a metabolite and can form unique stem-loop or hairpin structures in response to the amount of the metabolite present. They have two distinct regions – a metabolite-binding aptamer and an expression platform.
The aptamer has high specificity for a particular metabolite which allows riboswitches to specifically regulate...
Types of RNA01:23

Types of RNA

Overview
Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs perform diverse functions and can be broadly classified as protein-coding or non-coding RNA. Non-coding RNAs play important roles in the regulation of gene expression in response to developmental and environmental changes. Non-coding RNAs in prokaryotes can be manipulated to develop more effective antibacterial drugs for human or animal use.
RNA...
Ribozymes02:47

Ribozymes

The term ribozyme is used for RNA that can act as an enzyme. Ribozymes are mainly found in selected viruses, bacteria, plant organelles, and lower eukaryotes. Ribozymes were first discovered in 1982 when Tom Cech’s laboratory observed Group I introns acting as enzymes. This was shortly followed by the discovery of another ribozyme, Ribonulcease P, by Sid Altman’s laboratory. Both Cech and Altman received the Nobel Prize in chemistry in 1989 for their work on ribozymes.
Ribozymes can be...
Transcriptional Regulation: Riboswitches01:23

Transcriptional Regulation: Riboswitches

Riboswitches are RNA elements that regulate gene expression by altering their secondary structures in response to specific effector molecules. These elements, located in the leader regions of certain mRNAs, act as transcriptional regulators by toggling between alternative conformations to control downstream gene expression. Riboswitch-mediated regulation is a precise mechanism for modulating biosynthetic pathways, as exemplified by the riboflavin biosynthesis pathway in Bacillus...
Bacterial RNA Polymerase00:43

Bacterial RNA Polymerase

Unlike eukaryotes, bacteria use a single RNA Polymerase (RNAP) to transcribe all genes. The different subunits of bacterial RNAPhave distinct functions. The multisubunit structure of the bacterial RNAP helps the enzyme to maintain catalytic function, facilitate assembly, interact with DNA and RNA, and self-regulate its activity.
In most genes, the transcription site is a single base present upstream of the coding sequence. Though RNAP is a catalytically efficient enzyme, it does not recognize...

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Related Experiment Video

Updated: Jun 12, 2026

Nanomanipulation of Single RNA Molecules by Optical Tweezers
06:59

Nanomanipulation of Single RNA Molecules by Optical Tweezers

Published on: August 20, 2014

Ribonucleotide reductases: substrate specificity by allostery.

Peter Reichard1

  • 1Department of Biochemistry, Medical Nobel Institute, Karolinska Institutet, Stockholm 17177, Sweden. peter.reichard@ki.se

Biochemical and Biophysical Research Communications
|May 25, 2010
PubMed
Summary
This summary is machine-generated.

Ribonucleotide reductases (RNRs) are essential enzymes for DNA replication, producing deoxynucleotides from ribonucleotides. Structural studies reveal how RNRs maintain a balanced supply of deoxynucleotides through allosteric regulation and radical mechanisms.

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Studying Ribonucleotide Incorporation: Strand-specific Detection of Ribonucleotides in the Yeast Genome and Measuring Ribonucleotide-induced Mutagenesis
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Studying Ribonucleotide Incorporation: Strand-specific Detection of Ribonucleotides in the Yeast Genome and Measuring Ribonucleotide-induced Mutagenesis

Published on: July 26, 2018

Related Experiment Videos

Last Updated: Jun 12, 2026

Nanomanipulation of Single RNA Molecules by Optical Tweezers
06:59

Nanomanipulation of Single RNA Molecules by Optical Tweezers

Published on: August 20, 2014

Studying Ribonucleotide Incorporation: Strand-specific Detection of Ribonucleotides in the Yeast Genome and Measuring Ribonucleotide-induced Mutagenesis
09:04

Studying Ribonucleotide Incorporation: Strand-specific Detection of Ribonucleotides in the Yeast Genome and Measuring Ribonucleotide-induced Mutagenesis

Published on: July 26, 2018

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Enzymology

Background:

  • Ribonucleotide reductases (RNRs) are crucial enzymes in all living organisms, responsible for synthesizing deoxynucleotides from ribonucleotides.
  • These enzymes ensure the balanced production of the four deoxynucleoside triphosphates (dNTPs) essential for DNA replication and repair.
  • Three distinct classes of RNRs exist, all employing a common radical mechanism involving a thiyl radical, but differing in radical generation strategies.

Purpose of the Study:

  • To elucidate the structural basis of substrate specificity and allosteric regulation in the three classes of RNRs.
  • To understand how effector molecules (ATP and dNTPs) modulate RNR activity and specificity.
  • To provide detailed insights into the conformational changes induced by effector and substrate binding.

Main Methods:

  • X-ray crystallography was employed to determine the structures of catalytic subunits from all three RNR classes.
  • Studies were conducted with enzymes in complex with allosteric effectors (ATP, dNTPs) and cognate substrates.
  • Comparative structural analysis was performed to identify key structural changes associated with effector binding and substrate specificity.

Main Results:

  • Structural studies revealed conserved and class-specific conformational changes upon effector binding in RNRs.
  • Crystallographic data delineated how allosteric effectors dictate substrate preference by altering the enzyme's active site architecture.
  • The findings provide a detailed molecular understanding of the intricate allosteric control mechanisms governing dNTP synthesis.

Conclusions:

  • The structural mechanisms underlying RNR allosteric regulation and substrate specificity are conserved across the three classes.
  • Understanding these mechanisms is vital for comprehending cellular dNTP homeostasis and DNA replication fidelity.
  • This research provides a foundation for potential therapeutic strategies targeting RNRs in various diseases.