Functional Characterization of the potRABCD Operon for Spermine and Spermidine Uptake and Regulation in Staphylococcus aureus

Spermine, a potent bactericidal polyamine, exerts a strong synergistic effect with β-lactams against methicillin-resistant Staphylococcus aureus. Transcriptome analysis revealed that the putative potRABCD operon for polyamine uptake and regulation exhibited significant fold change upon exposure to exogenous spermine. Properties of the PotABCD transporter in polyamine uptake were studied using wild-type and the pot deletion mutant. It was found that spermidine and spermine, but not putrescine, were the preferred substrates for the Pot system of high affinity. The PotR protein was purified from a recombinant strain of Escherichia coli, and binding of PotR to the pot regulatory region was demonstrated by electromobility shift assays. In summary, these results support the physiological function of PotR in regulation of the expression of PotABCD for spermidine and spermine uptake in S. aureus.