10.2 - Two Component Signal Transduction Systems

Question 1

What are the two components?

Answer 1

(1) HPK - histidine protein kinase

2) RR (Response regulator

Question 2

What is the role of the sensor kinase?

Answer 2

• Environmental signals will be received by a sensor kinase and this signal will trigger auto-phosphorylation of a histidine residue in the Histidine protein kinase domain of the sensor kinase.
  o The phosphate comes from ATP.

Question 3

What is the phosphate transdferred to?

Answer 3

An aspartate residue on the RR protein in the cytoplasm.

Question 4

What does the RR protein then bind to?

Answer 4

An operator sequence on DNA and either stimulate or repress transcription of the target genes by influencing the intrinsic promoter strength.

Question 5

What does RR interact with?

Answer 5

Alpha subunits of RNA pol.

Question 6

What does phosphatase do?

Answer 6

A phosphatase removes the phosphate from RR protein and down-regulates the system.

Question 7

Why do regular proteins interact with different parts the RNA pol

Answer 7

There is no amino acid motif to which all proteins bind. Proteins have very rich contact surfaces so almost all regulators that interact with RNA pol exploit a specific region on the pol to make unique contacts. Unusual surfaces can be exploited to make very specific contacts. Evolving a protein to make a complementary contact results in enabling 2 pts to interact and work together.

Question 8

What can RR alter?

Answer 8

RR will either alter the binding constant or the ability of the polymerase to unwind DNA.

Question 9

What type of bacteria will have few two-component systems?

Answer 9

Bacteria that live in a stable environment

Question 10

What type of bacteria will have many two-component systems?

Answer 10

Bacteria that live in complex environments

Question 11

How can two-component systems be activated?

Answer 11

During low phosphate, oxygen or nitrogen conditions, as well as when there is a need to make new porins, for example, during conditions of starvation when the bacterium needs to uptake more nutrients.

Question 12

What is example of a negative feedback loop?

Answer 12

trp

Question 13

What does trp bind to?

Answer 13

Trp binding to aporepressor makes holorepressor

Question 14

What does the holorepressor do?

Answer 14

Holorepressor binding to trp operator (O) greatly reduces transcription