The solute transport and binding profile of a novel nucleobase cation symporter 2 from the honeybee pathogen .

Here, we report that a novel nucleobase cation symporter 2 encoded in the genome of the honeybee bacterial pathogen reveals high levels of amino acid sequence similarity to the and uric acid and xanthine transporters. This transporter is named uric acid permease-like protein (PlUacP). Even though PlUacP displays overall amino acid sequence similarities, has common secondary structures, and shares functional motifs and functionally important amino acids with xanthine and uric acid transporters, these commonalities are insufficient to assign transport function to PlUacP. The solute transport and binding profile of PlUacP was determined by radiolabeled uptake experiments via heterologous expression in nucleobase transporter-deficient strains. PlUacP transports the purines adenine and guanine and the pyrimidine uracil. Hypoxanthine, xanthine, and cytosine are not transported by PlUacP, but, along with uric acid, bind in a competitive manner. PlUacP has strong affinity for adenine 7.04 ± 0.18 μm, and as with other bacterial and plant NCS2 proteins, PlUacP function is inhibited by the proton disruptor carbonyl cyanide m-chlorophenylhydrazone. The solute transport and binding profile identifies PlUacP as a novel nucleobase transporter.