Cloning, tissue distribution and functional characterization of the donkey (Equus asinus) oligopeptide transporter 2

Oligopeptide transporter 2 (PepT2) is an important transporter of oligopeptides. In the present study, we describe the molecular cloning, tissue distribution and functional characterization of a donkey (Equus asinus) PepT2. The cloned cDNA sequence was 2202 bp at full length, encoding a 733 amino acid peptide with a molecular weight of 81.9 kDa and a theoretical pI of 8.92. Bioinformatics analysis showed that the deduced peptide sequence possessed all the characteristic features of PepT2. The expression of PepT2 in the kidney and lung was significantly higher than that observed in the ileum, duodenum, jejunum, spleen, liver, heart and stomach. Functional characterization by heterologous expression in Chinese hamster ovary cells showed that the uptake of β-Ala-Lys-N-7-amino-4-methylcoumarin-3-acetic acid (β-Ala-Lys-AMCA) by donkey PepT2-Chinese hamster ovary cells was dependent on time, pH and substrate concentration, with a low Km value of 91.51 ± 14.14 μM and a maximum velocity of 41.37 ± 2.193 pmol/min/mg protein. In the present study, for the first time, the expression and functional characteristics of donkey PepT2 were evaluated, the results of which provide new insights and a better understanding of its crucial role in oligopeptide transport in donkeys.