title: Identification of a potential substrate binding domain in the mammalian peptide transporters PEPT1 and PEPT2 using PEPT1-PEPT2 and PEPT2-PEPT1 chimeras.
abstract: The mammalian peptide transporters PEPT1 and PEPT2 are energized by a transmembrane electrochemical H+ gradient and exhibit similar broad substrate specificity. These transporters however differ in their affinity for substrates, PEPT1 being a low-affinity transporter and PEPT2 being a high-affinity transporter. To identify the substrate binding domain in PEPT1 and PEPT2 which is responsible for the differing affinities, we constructed a series of PEPT1-PEPT2 and PEPT2-PEPT1 chimeras using an in vivo restriction site-independent procedure and determined their substrate affinities. A comparison of these kinetic data for different chimeras with those of the wild-type PEPT1 and PEPT2 in conjunction with the specific structural PEPT1/PEPT2 crossover regions in these chimeras has led to the identification of a putative substrate binding site, which is comprised of the transmembrane domains 7, 8 and 9 of the transporters.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta 30912-2100, USA.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Fei
authors.forename: J C
authors.initials: JC
authors.lastname: Liu
authors.forename: T
authors.initials: T
authors.lastname: Fujita
authors.forename: R
authors.initials: R
authors.lastname: Liang
authors.forename: V
authors.initials: V
authors.lastname: Ganapathy
authors.forename: F H
authors.initials: FH
authors.lastname: Leibach
mesh_terms: D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials; D009865:Oocytes / Q000378:metabolism; D000074011:Peptide Transporter 1; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D027981:Symporters; D014982:Xenopus laevis
chemical_list: D002352:Carrier Proteins; D000074011:Peptide Transporter 1; D011993:Recombinant Fusion Proteins; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2