Question

Bacteria have specialized Two component system for the signaling, which among these is the part or sensory domain

• A. Histidine kinase
• B. Aspartate kinase
• C. Serine kinase
• D. Tyrosine kinase

Hint:

Remember the flow in a bacterial two-component system: Signal \(\rightarrow\) Sensor (Histidine Kinase) \(\rightarrow\) Phosphoryl group transfer \(\rightarrow\) Response Regulator (Aspartate phosphorylation) \(\rightarrow\) Change in gene expression.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Bacterial two-component signal transduction (TCS) is a basic stimulus-response mechanism that allows bacteria to sense and respond to changes in their environment. It consists of two main proteins: a sensor kinase and a response regulator.
Step 2: Detailed Explanation:
The two components are:
Sensor Kinase: This is typically a transmembrane protein. Its extracellular domain acts as the "sensory domain," which detects a specific environmental stimulus (like a nutrient, toxin, or osmotic pressure). The intracellular domain has kinase activity. Upon sensing a stimulus, this intracellular domain autophosphorylates a specific histidine residue. This is why the sensor kinase is specifically a Histidine Kinase.
Response Regulator: The phosphoryl group from the histidine on the sensor kinase is then transferred to an aspartate residue on the second component, the response regulator. This phosphorylation activates the response regulator, which then typically binds to DNA to alter gene expression, leading to a cellular response.
Therefore, the sensory domain is part of the Histidine Kinase component of the system. Aspartate is involved in the response regulator, while serine and tyrosine kinases are more characteristic of eukaryotic signaling.
Step 3: Final Answer:
The Histidine kinase acts as the sensor in a bacterial two-component system.