Two-component regulatory system

Two-component system (two- component system, TCS) referred to in cell biology a fairly general system of relaying information of interest in a cell.

Living cells are dependent on that external signals indicating a change in the environment ( ie, for example, a change in pressure or gradient of food molecules), passed into the cell. This process, called signal transduction allows the cell to respond appropriately to the signal. In many cells for this purpose, a scheme is employed in which, inter alia, two protein components are involved, which always assume the same function. We speak of a two-component system. Two -component systems are not found in bacteria, archaebacteria, eukaryotic unicellular fungi and higher plants, but in mammalian cells.

Most two-component systems consist of a transmembrane protein which acts as a sensor and a cytoplasmic protein that controls the regulation of a process in bacteria. The sensor protein is responsive to an external signal by a phosphate group is bound to a specific site of the protein. Specifically, it is phosphorylated histidine. The sensor protein is thus simultaneously a kinase, which is why it is also called sensor kinase. In a second step, the phosphate group is transferred to the regulatory protein, which is activated thereby. The activated regulatory protein is engaged in the gene expression in the control. An exception is chemotaxis, in which the regulatory protein directly affects the swimming direction of the bacterium.

In higher cells, the process is more complicated, since more components are involved. This allows cells to a more finely graded response to an external stimulus.

Examples of two-component systems

• ArcBA
• Histidine kinase
• NarXL system
• Regulation of metabolic pathways

• Signal transduction