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Section 8.11.1: The lac Operon. Early insights into mechanisms of transcriptional regulation came from studies of E. coli by researchers Francois Jacob & Jacques Monod. In E. coli, and many other bacteria, genes encoding several different proteins may be located on a single transcription unit called an operon.
The lac operon consists of a promoter (P) and operator (O) region followed by three structural genes lacZ, lacY, and lacA in the downstream. A regulatory gene lacI (I) preceding the lac operon is responsible for producing a repressor (R) protein.
The latter encode proteins required for the transport and metabolism of lactose: β-galactosidase (LacZ), lactose permease (LacY), and thiogalactosidase transacetylase (LacA). Further discussion will focus on the functions and structures of the two regulatory proteins, LacI, and CRP.
The lactose (lac) operon is a group of genes involved in lactose metabolism. They are found in bacteria, most notably Escherichia coli (E. coli), that use lactose as the alternate energy source when glucose is absent. The bacteria express the lac operon genes to use lactose, which encodes key enzymes for lactose uptake and metabolism.
The lactose operon is a set of genes in bacteria, such as E. coli, that are responsible for the uptake and metabolism of lactose. It consists of structural genes like lacZ, lacY, and lacA, which encode specific proteins involved in lactose utilization.
Lactose (lac) Operon. The prototype for negative regulation is the system in E. coli for metabolizing lactose (lac) ( Figure 24-1 ). The key chemical reaction carried out by the lac system is a cleavage of lactose to galactose and glucose.
A major type of gene regulation that occurs in prokaryotic cells utilizes and occurs through inducible operons. Inducible operons have proteins that can bind to either activate or repress transcription depending on the local environment and the needs of the cell. The lac operon is a typical inducible operon.
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 ...
The lactose or lac operon of Escherichia coli is a cluster of three structural genes encoding proteins involved in lactose metabolism and the sites on the DNA involved in the regulation of the operon. Many protein -coding genes in bacteria are clustered together in operons which serve as transcriptional units that are coordinately regulated.
Figure 1. Simplified schematic of the lac operon. When lactose is present and glucose concentrations are low the LacI protein binds with allolactose, and the rest of the operon is expressed. It is worth noting that the lac operon is also expressed when analogues of lactose like isopropyl β‑D-1-thiogalactopyranoside (IPTG) are present.