N-terminal halves of rat H+/peptide transporters are responsible for their substrate recognition.
OBJECTIVE
Peptide transporters PEPT1 and PEPT2 differ substantially in their substrate affinity and recognition. The aim of this study is to define the structural domains which influence the functional characteristics of both transporters


METHODS
Two kinds of chimeric peptide transporters (PEPT-N1C2 and PEPT-N2C1) were constructed, and their functional characteristics were compared with those of wild-type transporters in stable transfectants.


RESULTS
PEPT-N1C2, the N-terminal half of rat PEPT1 and the C-terminal half of rat PEPT2, and the reciprocal chimera PEPT-N2C1 were functionally expressed in LLC-PK1 cells. The pH-profiles of [14C] glycylsarcosine uptake by PEPT-N1C2 and PEPT-N2C1 were close to those of PEPT1 and PEPT2, respectively. Substrate recognition for PEPT-N1C2 and PEPT-N2C1 was also similar to that of PEPT1 and PEPT2, respectively. However, substrate affinities for PEPT-N1C2 were higher than those for PEPT1, although those for PEPT-N2C1 and PEPT2 were comparable.


CONCLUSIONS
These results indicate that functional regions which are associated with the extracellular pH changes and are responsible for substrate recognition of PEPT1 and PEPT2 may be located in the N-terminal halves of the proteins. In addition, it is suggested that the domain to affect the substrate affinity exists in the C-terminal as well as in the N-terminal half of rat PEPT2.
Terada
T
T
Department of Pharmacy, Kyoto University Hospital, Faculty of Medicine, Japan.
Saito
H
H
Sawada
K
K
Hashimoto
Y
Y
Inui
K
K
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D002478:Cells, Cultured; D004151:Dipeptides / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007769:Lactams; D000074011:Peptide Transporter 1; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D013379:Substrate Specificity; D027981:Symporters
D000900:Anti-Bacterial Agents; D002352:Carrier Proteins; D004151:Dipeptides; D007769:Lactams; D000074011:Peptide Transporter 1; D011993:Recombinant Fusion Proteins; C489940:Slc15a1 protein, rat; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2; C004194:glycylsarcosine