Two component systems

Question 1

What are two component systems (TCS)?

Answer 1

systems found in nearly all bacterial genomes which sense and respond to the environment
-bact can have lots of them (no. roughly proportional to size of genome)

Question 2

What is the structure of a two component system?

Answer 2

sensor: histidine kinase (oft membrane bound, containing intrinsic catalytic ATPase)
effector: response regulator

can have additional domains
in HK…
-PAS and GAF domains (bind small ligands)
-HAMP domain (transmits conf change)
in RR…
-reciever domain
-DNA-binding domain
-AAA+ ATPase activity
etc

Question 3

What accessory proteins are involved in two component systems?

Answer 3

-separate sensory protein (acts as sensor)
-scaffold proteins (facilitates phosphoryl transfer from HK to RR)
-connector proteins (communicates between 2 diff TCSs)
-allostery (RR doesn’t have its own output but feeds into another TCS)

Question 4

How have two component systems evolved?

Answer 4

-gene duplication
-generates two identical pathways which can cross-talk (phospho-transfer)
-mutations accumulate
-two pathways become separate (due to mutations in specificity-determining residues)