The di-aromatic pentapeptide repeats of the human peroxisome import receptor PEX5 are separate high affinity binding sites for the peroxisomal membrane protein PEX14.
PEX5 functions as a mobile import receptor for peroxisomal matrix proteins with a peroxisomal targeting signal 1 (PTS1). A critical step within the PTS1-import pathway is the interaction between PEX5 and the peroxisome membrane-associated protein PEX14. Based on two-hybrid analyses in mammalian cells and complementary in vitro binding assays, we demonstrate that the evolutionarily conserved pentapeptide repeat motifs, WX(E/D/Q/A/S)(E/D/Q)(F/Y), in PEX5 bind to PEX14 with high affinity. The results obtained indicate that each of the seven di-aromatic pentapeptides of human PEX5 interacts separately at the same binding site in the N terminus of PEX14 with equilibrium dissociation constants in the low nanomolar range. Mutational analysis of the PEX14-binding motifs reveals that the conserved aromatic amino acids at position 1 or 5 are essential for high affinity binding. We propose that the side chains of the aromatic amino acids are in close proximity as part of an amphipathic alpha-helix and together form hydrophobic anchors for binding PEX5 to individual PEX14 molecules.
Saidowsky
J
J
Institut für Physiologische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Dodt
G
G
Kirchberg
K
K
Wegner
A
A
Nastainczyk
W
W
Kunau
W H
WH
Schliebs
W
W
D020816:Amino Acid Motifs; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D000074435:Peroxisome-Targeting Signal 1 Receptor; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry* / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D012097:Repressor Proteins
D002352:Carrier Proteins; D008565:Membrane Proteins; C455539:PEX14 protein, human; C000614264:PEX5 protein, human; D000074435:Peroxisome-Targeting Signal 1 Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D012097:Repressor Proteins