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Two-Component Signal Transduction - most prokaryotic signal-transduction system and few eukaryotic pathways fall into this category

Basic steps

  1. autophosphorylation: HK-His + ATP <=> HK-His-P +ADP
  2. phosphotransfer: HK-His-P + RR-Asp <=> HK-His + RR-ASP-P
  3. dephosphorylation: RR-Asp-P + H20 <=> RR-Asp + Pi

-Starts with histidine protein kinase (HK)

  HK sense environmental stimuli and autophosphorylates at it's histidine residue
  HK has kinase core 
  Environmental stimuli sensing mechnism not very well characterized
  N-terminal of HK is sensing domain
  Sensing domain is connected to cytoplasmic kinase core through 
  transmembrane helix and a cytoplasmic linker

-HK transfers phosphate to aspartate residue on response regulator (RR)

  RR catalyzes phosphoryl transfer from HK
  Phosphorylation results in confomational change in RR and effects response
  RR also also catalyze autodephosphoylation
  RR has 2 domains: N-terminal regulatory domain and a C-terminal effector domain (DNA binding)