Two component systems are conserved among the bacteria, yeast, fungi and plants. ANIMALS do not have this system. It consists of 2 components in bacteria since they do not have a nucleus and three components in yeast (need more control). This system is a signal transduction stystem that senses developmental and enviromental stimuli.
The first component of this system 1) HISTIDINE KINASE has a conserved histidine that upon reception of signal is dimerized and is autophosphorylated at the histidine residue. This phosphorylation is a N- phosphoramidate bond (very unstable) in which the phospho groups are then transferred to the receiver domain on a conserved asparate residue on the 2) response regulator. This then activates its output domain and activates transcription (response). In yeast and plants the histidine kinase now has a receiver domain with the conserved asparate residue. Also the system has an added component the Histidine phosphotransmitter that receives the phospho group from the asparate residue on its histidine residue, which then transfers it to the response regulator on the receiver domain. The receiver domain then activates the output domain following with an activation of transcription or activation of a MAPK signal trasnsduction resonse.
