The same catabolite activator protein (CAP) involved with the lac operon interac

Question

The same catabolite activator protein (CAP) involved with the lac operon interacts with the ath operon ased on this information, how is the ath operon most likely controlled? rag the labels onto the diagram to identify the small molecules and the states of the regulatory proteins. Not all labels will be used. active repressor repressor repressor repressor activator activator inactive inactive inactive active helose CAMPglucose ath operon small positive control regulat protein+molecule small negative control regulatory protein +molecule reset help Submit Hints My Answers Give Up Review Part 16

Explanation / Answer

Operon is the collection of regulated genes that coordinate with each other. The gene group consists of structural genes that code for enzymes, regulatory genes that code for repressors or activators and regulatory sites like operators and promoters. Regulation of the operon usually occurs by controlling the genes by another element.

The type of controlling the operon genes is determined by the response of the operon to a regulatory protein. If the regulation of the operon genes is done by using a repressor protein that blocks the gene expression, the type of gene control is called as negative control. In this case, the gene will be activated when the repressor is disarmed. If the regulation of the operon genes is done by using an activator protein or activator that accelerates the gene expression, the type of gene control is called as positive control.

Negative control

Operon genes express when repressor is inactivated. Genes stop expressing in the presence of active repressor.

Positive control

Operon genes express when regulator protein is activated. Genes stop expressing when regulator protein is inactivated.

Positive control - Catabolite repression of ath operon

This is additional control system that works on repressor –operator system. This process exists because of the presence of the cellular enzymes that influence the uptake and metabolism of glucose.

Generally, presence of a substrate such as lactose in lac operon is responsible for the induction of operon function. Presence of glucose will not allow the operon to induce new machinery that metabolizes lactose into glucose for substrate induction. In the absence of glucose and in the presence of lactose, operon synthesizes an enzyme called beta-galactosidase. Inactivation of lac operon by lactose in the presence of glucose is called as Catabolite repression.

In the presence of excess of glucose, cAMP concentration decreases and when glucose is in low levels, cAMP concentration increases. High concentration of cAMP is required for the activation of lac operon. Organisms that do not have the genes expressing for the conversion of ATP into cAMP will not have induced lac operon to synthesize beta-galactosidase.

There are some other mutants that can synthesize cAMP and will not be able to induce lac enzymes. This happens due to the absence of Catabolite activator protein (CAP). CAP protein is produced by the crp gene. CAP will form a complex with cAMP and in turn attaches to the CAP site on the DNA. This CAP bound operon DNA, interacts with the RNA polymerase and enhances the affinity of RNA polymerase to the promoter of lac operon. Therefore, Catabolite repression system involves in the choosy activation of the lac operon.

The function of lactose in lac operon is done by athelose in ath operon. The functions of glucose and cAMP in lac operon are same as in ath operon.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.