Method for transducing protein-protein interactions

A mammalian cell comprising

• a first nucleic acid sequence encoding a first polypeptide fused to the N-terminus of a first variant of a histidine kinase comprising a dimerization and histidine-containing phosphotransfer (DHp) domain and a catalytic ATP-binding (CA) domain, wherein the first variant of the histidine kinase is a truncation variant that comprises neither a histidine kinase sensor domain nor a histidine kinase transmitter domain;
• a second nucleic acid sequence encoding a second polypeptide fused to the N-terminus of a second variant of said histidine kinase comprising a DHp domain and a CA domain, wherein the second variant of the histidine kinase is a truncation variant that comprises neither a histidine kinase sensor domain nor a histidine kinase transmitter domain;
• and
• a third nucleic acid sequence encoding a response regulatory protein specifically phosphorylatable by said DHp domain of said first or said second variant,
• wherein the histidine kinase belongs to the transphosphorylation family, wherein, upon specific binding of said first polypeptide and said second polypeptide, said first and second variants dimerize such that said CA domain of said first or second variant phosphorylates said DHp domain of said first or second variant, and the activity of said response regulatory protein is modulated by phosphorylation by said DHp domain of said first and/or second variant,
• and wherein:
• (a) each of said first and second variants comprises an amino acid sequence of SEQ ID NO:
• 11;
• or
• (b) said first variant comprises an amino acid sequence of SEQ ID NO:
• 12, and said second variant comprises an amino acid sequence of SEQ ID NO:
• 13.