title: Peroxin 5-peroxin 14 association in the protozoan Leishmania donovani involves a novel protein-protein interaction motif.
abstract: Import of proteins with a PTS1 (peroxisomal targeting signal 1) into the Leishmania glycosomal organelle involves docking of a PTS1-laden LdPEX5 [Leishmania donovani PEX5 (peroxin 5)] receptor to LdPEX14 on the surface of the glycosomal membrane. In higher eukaryotes, the PEX5-PEX14 interaction is mediated by a conserved diaromatic WXXXY/F motif. Site-directed and deletion mutageneses of the three WXXXY/F repeats in LdPEX5 did not abolish the LdPEX5-LdPEX14 association. Analysis of the equilibrium dissociation constant (K(d)) revealed that ldpex5-W53A (Trp53-->Ala), ldpex5-W293A, ldpex5-W176,293A and ldpex5-W53,176,293A mutant receptors were capable of binding LdPEX14 with affinities comparable with wild-type LdPEX5. That the diaromatic motifs were not required for the LdPEX5-LdPEX14 interaction was further verified by deletion analysis that showed that ldpex5 deletion mutants or ldpex5 fragments lacking the WXXXY/F motifs retained LdPEX14 binding activity. Mapping studies of LdPEX5 indicated that the necessary elements required for LdPEX14 association were localized to a region between residues 290 and 323. Finally, mutational analysis of LdPEX14 confirmed that residues 23-63, which encompass the conserved signature sequence AX2FLX7SPX6FLKGKGL/V present in all PEX14 proteins, are essential for LdPEX5 binding.
authors.affiliation: Institute of Parasitology, McGill University, Macdonald Campus, Ste. Anne de Bellevue, Quebec, Canada H9X 3V9.
authors.forename: Kleber P
authors.initials: KP
authors.lastname: Madrid
authors.forename: Armando
authors.initials: A
authors.lastname: Jardim
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D007893:Leishmania donovani / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D000074435:Peroxisome-Targeting Signal 1 Receptor; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017384:Sequence Deletion / Q000235:genetics; D017386:Sequence Homology, Amino Acid
chemical_list: C470663:PEX14 protein, Leishmania donovani; D000074435:Peroxisome-Targeting Signal 1 Receptor; D015800:Protozoan Proteins; D018160:Receptors, Cytoplasmic and Nuclear