Describe how the CbbR protein regulates its own transcription as well as that of the cbb operon in Xanthobacter flavus.

intro

CbbR protein

• functions as a transcriptional regulator

• controls

  • own expression

  • the transcription of the cbb operon,

• encodes

  • enzymes essential for the Calvin-Benson-Bassham (CBB) cycle of CO₂ fixation.

• is a LysR-type transcriptional regulator (LTTR).

  • binds to specific DNA sequences known as "CbbR boxes"

  • located in the promoter regions of the cbb operon and the cbbR gene itself.

  • binding occurs upstream of the -35 and -10 promoter elements

  • facilitates/inhibits the recruitment of RNA polymerase

In Xanthobacter flavus,

what does the CbbR protein functions as

a transcriptional regulator

what does the transcriptional regulator in Xanthobacter flavus, the CbbR protein control

its own expression

and

the transcription of the cbb operon,

In Xanthobacter flavus, the CbbR protein functions as a transcriptional regulator that controls both its own expression and the transcription of the cbb operon, which encodes ?

enzymes essential for the Calvin-Benson-Bassham (CBB) cycle of CO₂ fixation.

In Xanthobacter flavus, the CbbR protein functions as a transcriptional regulator that controls both its own expression and the transcription of the cbb operon, which encodes enzymes

what are these enzymes essential for?

the Calvin-Benson-Bassham (CBB) cycle of CO₂ fixation.

(CBB)

Calvin-Benson-Bassham

what kind of regulator is CbbR

a LysR-type transcriptional regulator (LTTR).

what does CbbR bind to

specific DNA sequences known as "CbbR boxes" located in the promoter regions of the cbb operon and the cbbR gene itself.

where are "CbbR boxes" located

in the promoter regions of the cbb operon and the cbbR gene itself.

CbbR is a LysR-type transcriptional regulator (LTTR). It binds to specific DNA sequences known as "CbbR boxes" located in the promoter regions of the cbb operon and the cbbR gene itself.

where does this binding typically occur

upstream of the -35 and -10 promoter elements

CbbR is a LysR-type transcriptional regulator (LTTR). It binds to specific DNA sequences known as "CbbR boxes" located in the promoter regions of the cbb operon and the cbbR gene itself.

what does this binding do

facilitates or inhibits the recruitment of RNA polymerase

CbbR is a LysR-type transcriptional regulator (LTTR).

It binds to specific DNA sequences known as "CbbR boxes" located in the promoter regions of the cbb operon and the cbbR gene itself.

This binding typically occurs upstream of the -35 and -10 promoter elements and facilitates or inhibits the recruitment of RNA polymerase, depending on ?

environmental conditions.

main points listed

Autoregulation of cbbR transcription

Regulation of the cbb operon

main point 1 Autoregulation of cbbR transcription:

• negatively regulated own transcription

• feedback inhibition.

• high intracellular levels of CbbR

• binds to the promoter region

• represses transcription

• maintain homeostatic levels of the regulator.

Autoregulation of cbbR transcription:

what does CbbR do to transcription

negatively regulates its own transcription through feedback inhibition.

Autoregulation of cbbR transcription

how does CbbR negatively regulates its own transcription

through feedback inhibition.

Autoregulation of cbbR transcription:

When intracellular levels of CbbR are high, what happens

it binds to the promoter region of the cbbR gene

represses further transcription,

Autoregulation of cbbR transcription:

When intracellular levels of CbbR are high, it binds to the promoter region of the cbbR gene and represses further transcription,

what does repressing further transcription do ?

maintaining homeostatic levels of the regulator.

main point 2

Regulation of the cbb operon:

• activates the transcription of the cbb operon

• response to low CO₂ /the presence of specific inducers

• ribulose-1,5-bisphosphate (RuBP).

• conformational change

• enhances its DNA-binding and promoter-activating capabilities.

• promotes transcription of genes encoding Calvin cycle enzymes, ( ribulose-1,5-bisphosphate), carboxylase/oxygenase (RuBisCO),

• facilitating open complex formation with RNA polymerase.

main point 2 Regulation of the cbb operon:

• CbbR in regards to transcription

• activates the transcription of the cbb operon

main point 2 Regulation of the cbb operon:

CbbR activates the transcription of

the cbb operon

main point 2 Regulation of the cbb operon:

• CbbR activates the transcription of the cbb operon in response to

• low CO₂

• or the presence of specific inducers such as ribulose-1,5-bisphosphate (RuBP).

main point 2 Regulation of the cbb operon:

Upon sensing these conditions,

CbbR undergoes

a conformational change that enhances its DNA-binding and promoter-activating capabilities.

main point 2 Regulation of the cbb operon:

Upon sensing these conditions, CbbR undergoes a conformational change that

enhances its DNA-binding and promoter-activating capabilities.

main point 2 Regulation of the cbb operon:

the conformational change

promotes

transcription of genes encoding Calvin cycle enzymes,

main point 2 Regulation of the cbb operon:

the conformational change

promotes transcription of genes encoding

Calvin cycle enzymes, such as ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO),

main point 2 Regulation of the cbb operon:

the conformational change

promotes transcription of genes encoding Calvin cycle enzymes, such as

ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO),

main point 2 Regulation of the cbb operon:

the conformational change

promotes transcription of genes encoding Calvin cycle enzymes, such as ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO),

by facilitating

open complex formation with RNA polymerase.

ending / summary

• CbbR ensures coordinated expression of CO₂ fixation genes and its own gene

• through dual regulatory mechanisms: negative autoregulation and positive regulation of the cbb operon in response to environmental cues.

CbbR ensures

coordinated expression of CO₂ fixation genes and its own gene

In summary, CbbR ensures coordinated expression of CO₂ fixation genes and its own gene through

dual regulatory mechanisms

CbbR ensures coordinated expression of CO₂ fixation genes and its own gene through dual regulatory mechanisms:

negative autoregulation and positive regulation of the cbb operon

CbbR ensures coordinated expression of CO₂ fixation genes and its own gene through dual regulatory mechanisms: negative autoregulation and positive regulation of the cbb operon in response to

environmental cues.

intro

Q: What is the role of CbbR in Xanthobacter flavus?
A:

It is a transcriptional regulator that controls its own expression and the cbb operon, essential for the Calvin-Benson-Bassham (CBB) cycle.

BODY PARAGRAPH 1: CbbR Structure and DNA Binding

What type of transcriptional regulator is CbbR?
A:

A LysR-type transcriptional regulator (LTTR).

BODY PARAGRAPH 1: CbbR Structure and DNA Binding

Where does CbbR bind on the DNA?
A:

It binds to "CbbR boxes" in the promoter regions of both the cbb operon and cbbR gene.

BODY PARAGRAPH 1: CbbR Structure and DNA Binding

What is the effect of CbbR binding to promoters?
A:

It can facilitate or inhibit RNA polymerase recruitment depending on environmental conditions.

BODY PARAGRAPH 2: Autoregulation of cbbR

How does CbbR regulate its own transcription?
A:

Through negative autoregulation (feedback inhibition).

BODY PARAGRAPH 2: Autoregulation of cbbR

What happens when CbbR levels are high?
A:

It binds its own promoter and represses transcription to maintain homeostasis.

BODY PARAGRAPH 3: Regulation of the cbb Operon

Flashcard 7
Q: What triggers CbbR to activate the cbb operon?
A:

Low CO₂ levels or the presence of ribulose-1,5-bisphosphate (RuBP).

BODY PARAGRAPH 3: Regulation of the cbb Operon

What happens to CbbR in response to these inducers?
A:

It undergoes a conformational change that enhances DNA binding and activation.

BODY PARAGRAPH 3: Regulation of the cbb Operon

How does CbbR promote transcription of Calvin cycle genes?
A:

By aiding RNA polymerase in forming the open complex for transcription initiation.

CONCLUSION

What is the dual regulatory role of CbbR?
A:

It represses its own gene and activates the cbb operon in response to environmental cues, ensuring coordinated CO₂ fixation.

What acronym helps remember CbbR’s roles?
A:

AR-OP

Autoregulation Repression – Operon Promotion
(Autorepression of cbbR - Promotion of cbb operon under CO₂ stress)