The proton-dependent oligopeptide transporter Ptr_C serves as an efficient system for antifungal delivery into Candida auris.

Aims: PTR transporters mediate the uptake of dipeptides/tripeptides as well as peptidomimetic drugs across diverse organisms, including bacteria, yeast, and humans. Our previous study identified three PTR transporters in Candida auris, with Ptr_C serving as a key player in the uptake of peptide substrates, including the antifungal, l-norvalyl-N3-(4-methoxyfumaroyl)-l-2,3-diaminopropanoic acid (Nva-FMDP). This study aims to evaluate the efficacy of different FMDP-based antifungal variants against C. auris, investigate the contribution of Ptr_C in their uptake, and establish a heterologous system to screen for peptide-based inhibitors that exploit Ptr_C for cellular entry.

Methods and results: In this study, utilizing deletion mutants of C. auris PTR transporters, we demonstrate that Ptr_C is the primary transporter facilitating the uptake of FMDP-based antifungal peptides. Furthermore, we developed a Ptr_C overexpression system in Saccharomyces cerevisiae, enabling rapid identification of antifungal peptides capable of exploiting this transporter using simplistic growth-based assays. The system's competence was further validated by constructing a few key site-directed mutants that alter the functional specificity of Ptr_C.