Peptide Selectivity of the Proton-Coupled Oligopeptide Transporter from Neisseria meningitidis.

Peptide transport in living organisms is facilitated by either primary transport， hydrolysis of ATP， or secondary transport， cotransport of protons. In this study， we focused on investigating the ligand specificity of the Neisseria meningitidis proton-coupled oligopeptide transporter (NmPOT). It has been shown that the gene encoding this transporter is upregulated during infection. NmPOT conformed to the typical chain length preference as observed in prototypical transporters of this family. In contrast to prototypical transporters， it was unable to accommodate a positively charged peptide residue at the C-terminus position of the substrate peptide. Sequence analysis of the active site of NmPOT displayed a distinctive aromatic patch， which has not been observed in any other transporters from this family. This aromatic patch may be involved in providing NmPOT with its atypical preferences. This study provides important novel information towards understanding how these transporters recognize their substrates.