title: Uridine recognition motifs of human equilibrative nucleoside transporters 1 and 2 produced in Saccharomyces cerevisiae.
abstract: The sugar moiety of nucleosides has been shown to play a major role in permeant-transporter interaction with human equilibrative nucleoside transporters 1 and 2 (hENT1 and hENT2). To better understand the structural requirements for interactions with hENT1 and hENT2, a series of uridine analogs with sugar modifications were subjected to an assay that tested their abilities to inhibit [3H]uridine transport mediated by recombinant hENT1 and hENT2 produced in Saccharomyces cerevisiae. hENT1 displayed higher affinity for uridine than hENT2. Both transporters barely tolerated modifications or inversion of configuration at C(3'). The C(2')-OH at uridine was a structural determinant for uridine-hENT1, but not for uridine-hENT2, interactions. Both transporters were sensitive to modifications at C(5') and hENT2 displayed more tolerance to removal of C(5')-OH than hENT1; addition of an O-methyl group at C(5') greatly reduced interaction with either hENT1 or hENT2. The changes in binding energies between transporter proteins and the different uridine analogs suggested that hENT1 formed strong interactions with C(3')-OH and moderate interactions with C(2')-OH and C(5')-OH of uridine, whereas hENT2 formed strong interactions with C(3')-OH, weak interactions with C(5')-OH, and no interaction with C(2')-OH.
authors.affiliation: Membrane Protein Research Group, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Mark F
authors.initials: MF
authors.lastname: Vickers
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Frank
authors.initials: F
authors.lastname: Visser
authors.forename: Tracey
authors.initials: T
authors.lastname: Tackaberry
authors.forename: Morris J
authors.initials: MJ
authors.lastname: Robins
authors.forename: Lars P C
authors.initials: LP
authors.lastname: Nielsen
authors.forename: Ireneusz
authors.initials: I
authors.lastname: Nowak
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Baldwin
authors.forename: James D
authors.initials: JD
authors.lastname: Young
authors.forename: Carol E
authors.initials: CE
authors.lastname: Cass
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D003001:Cloning, Molecular; D033721:Equilibrative Nucleoside Transporter 1 / Q000737:chemistry / Q000378:metabolism*; D033722:Equilibrative-Nucleoside Transporter 2 / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D012441:Saccharomyces cerevisiae; D013816:Thermodynamics; D014529:Uridine / Q000378:metabolism*
chemical_list: D033721:Equilibrative Nucleoside Transporter 1; D033722:Equilibrative-Nucleoside Transporter 2; C438649:SLC29A1 protein, human; C438654:SLC29A2 protein, human; D014529:Uridine