linda - two component systems Flashcards
(25 cards)
What is the main function of two-component regulatory systems in bacteria?
They detect environmental changes and trigger appropriate internal responses, typically via gene expression changes.
What types of environmental signals can two-component systems detect?
Changes in pH, oxygen levels, and osmolarity.
What are the two proteins involved in a two-component system?
A sensor kinase (in the membrane) and a response regulator (in the cytoplasm).
What is another name for a sensor kinase?
Histidine kinase.
What does the sensor kinase do when it senses a signal?
It autophosphorylates a histidine residue using a phosphate from ATP.
What happens after the sensor kinase is phosphorylated?
It transfers the phosphate to the response regulator.
What does the phosphorylated response regulator do?
It activates or represses target gene expression.
Can a response regulator act as both a repressor and activator?
Yes, depending on the target gene.
Why is osmoregulation important in E. coli?
To maintain a balance between internal and external osmotic pressure for cell stability.
How does osmosis work in bacterial cells?
Water moves across membranes from high to low water potential to balance solute concentrations.
What is the EnvZ/OmpR system responsible for?
Regulating porin expression in response to changes in environmental osmolarity.
What are porins?
Outer membrane proteins that allow solute transport.
What is OmpF?
A porin with a large pore, expressed under low osmolarity.
What is OmpC?
A porin with a smaller pore, expressed under high osmolarity.
What is the sensor kinase in the EnvZ/OmpR system?
EnvZ, an inner membrane protein.
What is the response regulator in the EnvZ/OmpR system?
OmpR, which regulates porin gene expression.
What does EnvZ do under osmotic stress?
It autophosphorylates and transfers the phosphate to OmpR.
What is OmpR-P?
The phosphorylated form of OmpR that can bind DNA to regulate porin genes.
What does OmpR-P do under low osmotic pressure?
Activates expression of ompF (large pore porin) and has no effect on ompC.
What does OmpR-P do under high osmotic pressure?
Activates ompC expression and represses ompF expression.
Why express OmpC under high osmotic pressure?
Smaller pores reduce solute influx, protecting the cell.
Why express OmpF under low osmotic pressure?
Larger pores facilitate nutrient uptake when solute stress is low.
How does phosphorylation affect OmpR’s function?
It activates OmpR, allowing it to bind DNA and regulate gene expression.
What role does ATP play in this two-component system?
It donates the phosphate used by the sensor kinase to autophosphorylate.
