The effects of L-arginine on protein stability and DNA binding ability of SaeR, a transcription factor in Staphylococcus aureus

The SaeRS two-component system in Staphylococcus aureus controls the expression of a series of virulence factors, such as hemolysins, proteases, and coagulase. The response regulator, SaeR, belongs to the OmpR family with an N-terminal regulatory domain and a C-terminal DNA binding domain. To improve the production and stability of the recombinant protein SaeR, l-arginine (L-Arg) was added to the purification buffers. L-Arg enhanced the solubility and stability of the recombinant protein SaeR. The thermal denaturation temperature of SaeR in 10 mM L-Arg buffer was significantly increased compared to the buffer without L-Arg. Microscale Thermophoresis (MST) analysis results showed that the SaeR protein could bind to the P1 promoter under both phosphorylated and non-phosphorylated status in buffer containing 10 mM L-Arg. These results illustrate an effective method to purify SaeR and other proteins.