Related Experiment Video
Updated: Jul 7, 2026
05:03
Quantitative Analysis of Dietary Vitamin A Metabolites in Murine Ocular and Non-Ocular Tissues Using High-Performance Liquid Chromatography
Published on: December 27, 2024
Identification, characterization, and structure/function analysis of a corrin reductase involved in adenosylcobalamin
Andrew D Lawrence1, Evelyne Deery, Kirsty J McLean
1Protein Science Group, Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom.
The Journal of Biological Chemistry
|February 12, 2008
Summary
Researchers identified the CobR enzyme, crucial for Vitamin B12 biosynthesis. This flavoprotein facilitates the reduction of cobalt ions, a key step in creating this essential coenzyme.
Area of Science:
- Biochemistry
- Enzymology
- Microbiology
Background:
- Vitamin B12 (cobalamin) is a complex coenzyme synthesized via aerobic and anaerobic pathways.
- Adenosylcobalamin biosynthesis requires reduction of cobalt from Co(II) to Co(I).
Purpose of the Study:
- To identify and characterize the enzyme responsible for cobalt reduction in the aerobic cobalamin biosynthesis pathway.
- To elucidate the mechanism of the cobalt(II)rrin reductase activity.
Main Methods:
- Cloning and overproduction of the cobR gene from Brucella melitensis.
- Purification and characterization of the CobR flavoprotein.
- X-ray crystallography for structure determination (1.6A resolution).
- Kinetic and Electron Paramagnetic Resonance (EPR) analysis.
Main Results:
- The cobR gene encodes a functional cobalt(II)rrin reductase.
- The purified CobR enzyme is a flavoprotein that proceeds via a semiquinone intermediate.
- The crystal structure of CobR was determined at 1.6A resolution.
Conclusions:
- CobR is a key enzyme in the aerobic biosynthesis of Vitamin B12.
- The enzyme's mechanism involves a semiquinone form, facilitating cobalt reduction.
- CobR may interact with adenosyltransferase to overcome the thermodynamic barrier for cobalt reduction.
Related Concept Videos
01:23Transcriptional 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...
01:28Biosynthesis of Nucleic Acids
Nucleic acid biosynthesis is a fundamental biochemical process that produces the purine and pyrimidine nucleotides essential for DNA and RNA synthesis. This pathway maintains a balanced nucleotide pool, preventing imbalances that could jeopardize genetic integrity and cellular function. Given the crucial role of nucleotides, their synthesis is tightly regulated to ensure proper cellular homeostasis.Purine BiosynthesisThe biosynthesis of purine nucleotides begins with ribose-5-phosphate, a...
01:56Riboswitches
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...
The aptamer has high specificity for a particular metabolite which allows riboswitches to specifically regulate...
01:46The Calvin Benson Cycle
Ribulose 1,5- bisphosphate carboxylase/oxygenase (RuBisCo) is a critical enzyme that catalyzes carbon dioxide assimilation during photosynthesis. However, it is an inefficient enzyme, having an extremely slow catalytic rate. A typical enzyme can process about a thousand molecules per second; however, RuBisCo fixes only around three-carbon dioxides per second. Photosynthetic cells compensate for this slow rate by synthesizing very high amounts of RuBisCo, making it the most abundant single...
02:23RNA Editing
RNA editing is a post-transcriptional modification where a precursor mRNA (pre-mRNA) nucleotide sequence is changed by base insertion, deletion, or modification. The extent of RNA editing varies from a few hundred bases, in mitochondrial DNA of trypanosomes, to a just single base, in nuclear genes of mammals. Even a single base change in the pre-mRNA can convert a codon for one amino acid into the codon for another amino acid or a stop codon. This type of re-coding can significantly affect the...
01:29Role of Reduced Coenzymes NADH and FADH₂
The energy released from the breakdown of the chemical bonds within nutrients can be stored either through the reduction of electron carriers or in the bonds of adenosine triphosphate (ATP). In living systems, a small class of compounds functions as mobile electron carriers, molecules that bind to and shuttle high-energy electrons between compounds in pathways. The principal electron carriers that will be considered originate from the B vitamin group and are derivatives of nucleotides; they are...