Myxococcus xanthus Life cycle - A signal
The A-signal is also known as cell density signal. When the cells are starving and the cell density is sufficiently high for fruiting body formation and aggregation an A-signal is produced.
Blog by Mufaddal Dewaswala
The A-signal is also known as cell density signal. When the cells are starving and the cell density is sufficiently high for fruiting body formation and aggregation an A-signal is produced.
- The A-signal begins when there is a nutrient limitation; starvation for amino acids, carbon, phosphorus etc.
- An intracellular signal is activated and an intracellular signaling molecule ppGpp is synthesized.[ppGpp stands for guanosine 3'-diphosphate 5'-diphosphate]
- This intracellular signal activates a putative DNA binding protein called AsgB and a sigma factor for it called AsgC.
- AsgB (and AsgC as sigma factor) activate genes required for synthesis for certain proteases.
- Various proteases are made and are secreted. These proteases degrade the cell surface proteins into various amino-acids which are known as the A-signal.
- When the concentration of A-signal rises above 10 microM, a membrane bound histidine kinase is activated which is called SasS.
- SasS is autophosphorylated and it then phosophorylates a response regulator protein named SasR.
- SasR-P (phosphorylated SasR) stimulates transcription of gene named fruA.
- fruA gene makes FruA product. After which FruA is phosphorylated to form FruA-P by a putative histidine protein kinase(HPK).
- FruA-P activates various developmental genes which will lead to fruiting body formation and aggregation.
Blog by Mufaddal Dewaswala
