Identification of Leishmania Donovani Peroxin 14 Residues Required for Binding the Peroxin 5 Receptor Proteins

Trafficking of peroxisomal targeting signal 1 (PTS1) proteins to the Leishmania glycosome is dependent on the docking of the LdPEX5 receptor to LdPEX14 on the glycosomal membrane. A combination of deletion and random mutagenesis was used to identify residues in the LdPEX14 N-terminal region that are critical for mediating the LdPEX5-LdPEX14 interaction. These studies highlighted residues 35-75 on ldpex14 as the core domain required for binding LdPEX5. Single point mutation within this core domain generally did not affect the ldpex5( 203-391)-ldpex14-(1-120) interaction; notable exceptions were substitutions at Phe(40), Val(46) or Phe(57) which completely abolished or increased the apparent K-d value for ldpex5-(203-391) binding 30-fold. Biochemical studies revealed that these point mutations did not alter either the secondary or quaternary structure of LdPEX14 and indicated that the latter residues were critical for stabilizing the LdPEX5-LdPEX14 interaction.