title: FUN26 (function unknown now 26) protein from saccharomyces cerevisiae is a broad selectivity, high affinity, nucleoside and nucleobase transporter.
abstract: Equilibrative nucleoside transporters (ENTs) are polytopic integral membrane proteins that transport nucleosides and, to a lesser extent, nucleobases across cell membranes. ENTs modulate efficacy for a range of human therapeutics and function in a diffusion-controlled bidirectional manner. A detailed understanding of ENT function at the molecular level has remained elusive. FUN26 (function unknown now 26) is a putative ENT homolog from S. cerevisiae that is expressed in vacuole membranes. In the present system, proteoliposome studies of purified FUN26 demonstrate robust nucleoside and nucleobase uptake into the luminal volume for a broad range of substrates. This transport activity is sensitive to nucleoside modifications in the C(2')- and C(5')-positions on the ribose sugar and is not stimulated by a membrane pH differential. [(3)H]Adenine nucleobase transport efficiency is increased ∼4-fold relative to nucleosides tested with no observed [(3)H]adenosine or [(3)H]UTP transport. FUN26 mutational studies identified residues that disrupt (G463A or G216A) or modulate (F249I or L390A) transporter function. These results demonstrate that FUN26 has a unique substrate transport profile relative to known ENT family members and that a purified ENT can be reconstituted in proteoliposomes for functional characterization in a defined system.
authors.affiliation: From the Department of Biochemistry and Molecular Biology and.
authors.forename: Rebba C
authors.initials: RC
authors.lastname: Boswell-Casteel
authors.affiliation: From the Department of Biochemistry and Molecular Biology and.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Johnson
authors.affiliation: From the Department of Biochemistry and Molecular Biology and.
authors.forename: Kelli D
authors.initials: KD
authors.lastname: Duggan
authors.affiliation: the Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143.
authors.forename: Zygy
authors.initials: Z
authors.lastname: Roe-Žurž
authors.affiliation: From the Department of Biochemistry and Molecular Biology and.
authors.forename: Hannah
authors.initials: H
authors.lastname: Schmitz
authors.affiliation: From the Department of Biochemistry and Molecular Biology and.
authors.forename: Carter
authors.initials: C
authors.lastname: Burleson
authors.affiliation: From the Department of Biochemistry and Molecular Biology and the Stephenson Oklahoma Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104 and Franklin-Hays@ouhsc.edu.
authors.forename: Franklin A
authors.initials: FA
authors.lastname: Hays
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D033705:Equilibrative Nucleoside Transport Proteins / Q000378:metabolism*; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000378:metabolism / Q000502:physiology*; D016133:Polymerase Chain Reaction; D011510:Proteolipids; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology*; D012995:Solubility
chemical_list: D017931:DNA Primers; D033705:Equilibrative Nucleoside Transport Proteins; C558927:FUN26 protein, S cerevisiae; D026901:Membrane Transport Proteins; D011510:Proteolipids; D029701:Saccharomyces cerevisiae Proteins; C020485:proteoliposomes
keywords: Membrane Protein; Membrane Transport; Membrane Transporter Reconstitution; Nucleoside/Nucleotide Transport; Transporter