REGULATING AND SIGNALING

Flashcards about genetic regulation, signaling, and metabolic coordination.

How do cells know that they are low on phosphorus?

Through metabolic coordination and protein activity

What are two ways to control protein activity?

Allosteric change and reversible modification (covalent modification)

How does allosteric change affect protein velocity?

By binding a ligand to a site on a protein that is not the active site.

What is reversible modification?

Binding a phosphate onto a protein to control its activity.

What gives RNA polymerase specificity for the promoter?

Sigma factors.

How can the amount of protein be controlled via promoter recognition?

By changing the concentration of Sigma factors, which affects whether a protein is produced or not.

How do transcriptional repressors affect gene expression?

Active repressors decrease expression, while activators increase expression.

What are enhancers?

Regions that increase expression but are not near the promoter; they bind regulatory proteins somewhere else further away from the promoter.

What is the function of the lac operon?

It's involved in lactose metabolism in E. Coli and demonstrates regulation using activators and repressors.

What are structural genes in the lac operon?

lacZ, lacY, and lacA.

What does lacZ encode?

Beta-galactosidase.

What is the operator in the lac operon?

The region where the repressor (LacI) binds.

What is the role of the LacI repressor?

It binds to the operator and serves as a barrier, preventing RNA polymerase from transcribing genes.

How does allolactose affect LacI?

LacI binds to allolactose, making it inactive, so it won't bind to the operator and RNA polymerase can transcribe.

What happens to the lac operon when lactose is present but glucose concentration is very little?

Allolactose binds to LacI, preventing it from binding. Lots of beta-galactosidase will be produced

In E. Coli, which is the preferred substrate?

Glucose.

What is catabolite repression?

When one substrate represses the catabolism of another substrate.

What is the function of CAP?

It increases the efficiency of RNA polymerase binding to the promoter.

How does CAP assist RNA polymerase in binding to the promoter?

CAP causes the DNA helix to bend slightly, enabling CAP to bind to RNA polymerase.

What does CAP bind to?

cAMP.

What is cAMP?

A signaling molecule in bacteria used to regulate gene expression in response to the environment (e.g., glucose levels).

How is cAMP formed?

From ATP via adenylyl cyclase.

How does glucose affect cAMP levels?

Glucose inhibits adenylyl cyclase. Therefore, When glucose is present, less cAMP is formed.

What type of regulator is CAP when bound to cAMP?

A positive regulator (activator).

What type of regulator is LacI when bound to allolactose?

A negative regulator.

How does sRNA affect the transcription of DNA?

sRNA binds near the promoter and could affect the recognition of RNA polymerase to the promoter, block RNA polymerase from binding, or block regulators.

How does sRNA affect transcription through termination?

sRNA can terminate transcription by inducing a termination loop.

How does sRNA affect the stability of mRNA?

sRNA can alter the stability of mRNA; if mRNA is stable, it allows the opportunity to make lots of protein. If mRNA is unstable, the opportunity for making protein decreases.

How does sRNA affect translation?

sRNA can bind at the 5' end of mRNA, preventing translation.

How does DNA topology affect transcription?

Accessibility of DNA to transcription apparatuses. DNA must be accessible to RNA polymerase to get transcription.

Where does transcription occur?

At the interface of the nucleoid and cytoplasm.

What are translational repression and activation?

Regulatory proteins bind to mRNA.

What is attenuation?

When the structure of mRNA regulates transcription and is a mechanism for transcription termination, identified in the trp operon.

What does an attenuator consist of?

A leader sequence and an attenuator.

What is the function of the leader sequence?

It has two Trp codons, and the speed of translation/abundance of Trp tRNA controls the speed of translation.

How is transcription controlled based on the attenuator?

If translation is fast, a termination loop is created. If translation is slow, no terminator hairpin is formed.

How does mRNA stability affect protein production?

More stable mRNA leads to more protein production because it can be used as a template to make more protein.

How do small RNAs (sRNA) influence the stability of mRNA?

They can decrease the stability of mRNA by degrading it.

What is protein proteolysis?

Commonly applied to regulatory proteins, not metabolic enzymes.