Functional characterization of a Na+-coupled dicarboxylate carrier protein from staphylococcus aureus

We have cloned and functionally characterized a Na+-coupled dicarboxylate transporter, SdcS, from Staphylococcus aureus. This carrier protein is a member of the divalent anion/Na+ symporter (DASS) family and shares significant sequence homology with the mammalian Na+/dicarboxylate cotransporters NaDC-1 and NaDC-3. Analysis of SdcS function indicates transport properties consistent with those of its eukaryotic counterparts. Thus, SdcS facilitates the transport of the dicarboxylates fumarate, malate, and succinate across the cytoplasmic membrane in a Na+-dependent manner. Furthermore, kinetic work predicts an ordered reaction sequence with Na+ (K-0.5 of 2.7 mM) binding before dicarboxylate (K-m of 4.5 mu M). Because this transporter and its mammalian homologs are functionally similar, we suggest that SdcS may serve as a useful model for DASS family structural analysis.