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The lac operon of the model bacterium Escherichia coli was the first operon to be discovered and provides a typical example of operon function. It consists of three adjacent structural genes, a promoter, a terminator, and an operator. The lac operon is regulated by several factors including the availability of glucose and lactose.
The lactose operon (lac operon) is an operon required for the transport and metabolism of lactose in E. coli and many other enteric bacteria.Although glucose is the preferred carbon source for most enteric bacteria, the lac operon allows for the effective digestion of lactose when glucose is not available through the activity of β-galactosidase. [1]
Genetic regulatory circuits (also referred to as transcriptional regulatory circuits) is a concept that evolved from the Operon Model discovered by François Jacob and Jacques Monod. [1] [2] [3] They are functional clusters of genes that impact each other's expression through inducible transcription factors and cis-regulatory elements. [4] [5]
The Lac operon is an interesting example of how gene expression can be regulated. Viruses, despite having only a few genes, possess mechanisms to regulate their gene expression, typically into an early and late phase, using collinear systems regulated by anti-terminators ( lambda phage ) or splicing modulators ( HIV ).
The gal operon contains two operators, O E (for external) and O I (for internal). The former is just upstream of the promoter, and the latter is just after the galE gene (the first gene in the operon). These operators bind the repressor, GalR, which is encoded from outside the operator region. For this repressor protein to function properly ...
Monod joined the Pasteur Institute in 1943 and Jacob in 1949. The experimental system ultimately used by Jacob and Monod was a common bacterium, E. coli, but the basic regulatory concept (described in the Lac operon article) that was discovered by Jacob and Monod is fundamental to cellular regulation for all organisms.
Changes in the regulation of gene networks are a common mechanism for prokaryotic evolution.An example of the effects of different regulatory environments for homologous proteins is the DNA-binding protein OmpR, which is involved in response to osmotic stress in E. coli but is involved in response to acidic environments in the close relative Salmonella Typhimurium.
Structure of the trp operon. The trp operon is a group of genes that are transcribed together, encoding the enzymes that produce the amino acid tryptophan in bacteria. The trp operon was first characterized in Escherichia coli, and it has since been discovered in many other bacteria. [1]