ATP- and ADP-DnaA protein, a molecular switch in gene regulation

DnaA protein functions by binding to asymmetric 9mer DNA sites, the DnaA bo xes. ATP-DnaA and ADP-DnaA bind to 9mer DnaA boxes with equal affinity, but only ATP-DnaA protein binds in addition to an as yet unknown 6mer site, th e ATP-DnaA box AGATCT, or a close match to it, ATP-DnaA protein binding to ATP-DnaA boxes is restricted to sites located in close proximity to DnaA bo xes, suggesting that protein-protein interaction is required for its stabil ization. We show that ATP-DnaA represses dnaA transcription much more effic iently than ADP-DnaA. DnaA is thus a regulatory molecule that, depending on the adenosine nucleotide bound, can bind to different sequences and thereb y fulfill distinct functions.