78. Bacterial two component system includes
(1) Sensory kinase and response regulator
(2) Sensory kinase and Phosphotransferase
(3) Signal and receptor
(4) Stimulus and response

Bacterial Two-Component System: Sensor Kinase and Response Regulator

Introduction

The bacterial two-component system is a fundamental mechanism for sensing and responding to environmental changes. It enables bacteria to adapt quickly by regulating gene expression and physiological responses.

Core Components

Typically, the two-component system comprises two essential proteins:

1. Sensory Histidine Kinase (HK): This membrane-bound protein detects specific environmental stimuli. Upon activation, it autophosphorylates at a conserved histidine residue using ATP.

2. Response Regulator (RR): This cytoplasmic protein receives the phosphate group from the histidine kinase on a conserved aspartate residue. Phosphorylation induces conformational changes that activate the response regulator, often leading to changes in gene transcription.

Signal transduction involves the phosphate being transferred from HK to RR, linking external signals directly to changes in cellular behavior.

Variations and Function

• Some two-component systems include additional phosphotransfer steps (phosphorelays).

• They regulate diverse processes such as osmoregulation, nutrient sensing, quorum sensing, virulence, and stress responses.

• Bacteria often carry multiple two-component systems tailored to their ecological niches.

Summary of Options

Correct answer: (1) Sensory kinase and response regulator