Developmental regulation of a turkey intestinal peptide transporter (PepT1).

A cDNA encoding a turkey intestinal peptide transporter, tPepT1, was isolated from a turkey small intestinal cDNA library. The tPepT1 cDNA encodes a 714-amino acid protein with 12 predicted transmembrane domains. The amino acid sequence of tPepT1 is 94.3% identical to chicken PepT1 and approximately 60% identical to PepT1 from rat, sheep, rabbit, and human. Using a 2-electrode voltage-clamp technique in Xenopus oocytes expressing tPepT1, Gly-Sar transport was pH dependent but was independent of Na+ and K+. For the dipeptides Gly-Sar and Met-Met, the evoked inward currents indicated that the transporter was saturable and had high affinity (0.69 +/- 0.14 mM and 0.23 +/- 0.04 mM, respectively) for these substrates. However, transport of the tetrapeptide, Met-Gly-Met-Met, exhibited apparent substrate inhibition at high substrate concentrations. To study developmental regulation of PepT1 mRNA in turkey embryos, embryos (6 males and 6 females) were sampled daily from 5 d before hatch to the day of hatch (d 0). The abundance of PepT1 mRNA in the small intestine was quantified densitometrically from Northern blots after hybridization with full-length tPepT1 cDNA as probe. A 3.2-fold increase in PepT1 mRNA was observed in intestinal tissue from 5 d before hatch to d 0. This increase in PepT1 mRNA abundance indicates that the PepT1 gene is developmentally regulated and that there may be an important role for PepT1 in the neonatal poult.