Fig. 3. Unrooted phylogenetic tree depicting the evolutionary relationship of vertebrate PepT1 transporters. The unrooted tree was constructed using the neighbor-joining (NJ) method (Saitou and Nei, 1987) based on the alignment of the complete amino acid sequences of known vertebrate PepT1 transporters. Bootstrap values (1000 replicates) indicating the occurrence of nodes are reported above each branch in the figure.