The adjacent ATP-binding protein-encoding genes of the <i>Enterococcus faecalis</i> phosphate-specific transport ( <i>pst</i> ) locus have non-overlapping cellular functions

Phosphate is critical for all microbial life. In many bacteria, inorganic phosphate (Pi) is imported by the high-affinity, low-velocity Pst-PhoU system. The <i>pstB</i> gene encodes the ATPase that powers Pi import. The <i>pst-phoU</i> operon in many Firmicutes, including the human commensal and opportunistic pathogen <i>Enterococcus faecalis</i>, contains adjacent <i>pstB</i> genes, <i>pstB1</i> and <i>pstB2</i>. No studies on the relative biological contributions of tandem <i>pstB</i> paralogs in any microbe have been published. This genetic study indicates that <i>E. faecalis pstB1</i> and <i>pstB2</i> do not have equivalent functions. The <i>pstB2</i> gene encodes an ATPase that is required for Pi import, while the ATPase encoded by <i>pstB1</i> has an accessory role in Pi import that can be duplicated by the presence of excess PstB2.