Two-Component Regulatory System :

Two Component Regulatory System :

Bacteria can sense environmental and cytoplasmic signals and transmit information to the genome or other parts of the cell to elicit a response.

- Signal transduction pathway includes              histidine kinase protein that receives                signal and transmits it to partner 

  response regulatory protein.

- The response regulatory protein transmits       signal to the target.

- The signal is transmitted between HK and       RR through phosphorylation.

- The Histidine Kinase autophosphorylates        at histidine residue in response to stimulus    (ATP as Phosphoryl Donor) and then                transfer phosphoryl group to aspartate            residue.

- In the partner response regulator protein        this activates the response regulator(RR).

- The phosphorylated RR proteins stimulate       or repress the transcription of specific             genes.

- Signaling pathway also includes phosphate     which are dephosphorylates the RR,                 returning it to the non-stimulated state             where it can once again reapond to the           signal.

Note : HK - sometimes bifunctional enzymes that can act as Kinase/Phosphatases.When stimulation of HK promotes phosphatase actively results in dephosphorylation of RR & repression of transcription.

1) Cell membrane histidine kinase (HK) is             activated by signal at its N-terminal                 domain.

2) The activated protein autophosphorylates       in the C-terminal domain.

3) Then the response regulator protein                 (RR) binds to the C-terminal and of HK.

4) The phosphoryl group is transferred from         histidine kinase (HK) to response                     regulator after then RR activates.

5) The activated response regulator leaves           the histidine kinase (HK) and stimulates         its target.

6) Shaded areas of the histidine kinase                (HK) and response regulator protein                represent conserved amino acid sequence.

7) Change in the shape of the proteins                   represents a preassumed confirmational         change.

8) In some systems, histidine kinase (HK) is        a Cytoplasmic protein and detects signals      within the cytoplasm.