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Origin, diversification and substrate specificity in the family of NCS 1/ FUR transporters
Author(s) -
Krypotou Emilia,
Evangelidis Thomas,
Bobonis Jacob,
Pittis Alexandros A.,
Gabaldón Toni,
Scazzocchio Claudio,
Mikros Emmanuel,
Diallinas George
Publication year - 2015
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12982
Subject(s) - aspergillus nidulans , biology , transporter , transmembrane domain , biochemistry , homology modeling , gene , genetics , gene duplication , computational biology , enzyme , mutant
Summary NCS 1 proteins are H + / Na + symporters specific for the uptake of purines, pyrimidines and related metabolites. In this article, we study the origin, diversification and substrate specificity of fungal NCS 1 transporters. We show that the two fungal NCS 1 sub‐families, F ur and F cy, and plant homologues originate through independent horizontal transfers from prokaryotes and that expansion by gene duplication led to the functional diversification of fungal NCS 1. We characterised all F ur proteins of the model fungus A spergillus nidulans and discovered novel functions and specificities. Homology modelling, substrate docking, molecular dynamics and systematic mutational analysis in three Fur transporters with distinct specificities identified residues critical for function and specificity, located within a major substrate binding site, in transmembrane segments TMS 1, TMS 3, TMS 6 and TMS 8. Most importantly, we predict and confirm that residues determining substrate specificity are located not only in the major substrate binding site, but also in a putative outward‐facing selective gate. Our evolutionary and structure‐function analysis contributes in the understanding of the molecular mechanisms underlying the functional diversification of eukaryotic NCS 1 transporters, and in particular, forward the concept that selective channel‐like gates might contribute to substrate specificity.