Negative cooperativity within individual tetramers of Escherichia coli single strand binding protein is responsible for the transition between the (SSB)35 and (SSB)56 DNA binding modes.

We have examined the binding of the oligonucleotide dT (pT)34 to the Escherichia coli SSB protein as a function of NaCl and MgCl2 concentration (25 degrees C, pH 8.1) by monitoring the quenching of the intrinsic protein fluorescence. We find two binding sites for dT(pT)34 per single strand binding (SSB) protein tetramer, with each site possessing widely… (More)