Substrate Specificity of the FurE Transporter Is Determined by Cytoplasmic Terminal Domain Interactions.

ABSTRACT: FurE, a member of the Nucleobase Cation Symporter 1 transporter family in Aspergillus nidulans, is specific for allantoin, uric acid (UA), uracil, and related analogs. Herein, we show that C- or N-terminally-truncated FurE transporters (FurE-?C or FurE-??) present increased protein stability, but also an inability for UA transport. To better understand the role of cytoplasmic terminal regions, we characterized genetic suppressors that restore FurE-?C-mediated UA transport. Suppressors map in the periphery of the substrate-binding site [Thr133 in transmembrane segment (TMS)3 and Val343 in TMS8], an outward-facing gate (Ser296 in TMS7, Ile371 in TMS9, and Tyr392 and Leu394 in TMS10), or in flexible loops (Asp26 in L_N, Gly222 in L5, and Asn308 in L7). Selected suppressors were also shown to restore the wild-type specificity of FurE-??, suggesting that both C- and/or N-terminal domains are involved in intramolecular dynamics critical for substrate selection. A direct, substrate-sensitive interaction of C- and/or N-terminal domains was supported by bimolecular fluorescence complementation assays. To our knowledge, this is the first case where not only the function, but also the specificity, of a eukaryotic transporter is regulated by its terminal cytoplasmic regions.

SUBMITTER: Papadaki GF 

PROVIDER: S-EPMC5714455 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature