Insertion of Pex5p into the peroxisomal membrane is cargo protein-dependent.
It is now generally accepted that Pex5p, the receptor for most peroxisomal matrix proteins, cycles between the cytosol and the peroxisomal compartment. According to current models of peroxisomal biogenesis, this intracellular trafficking of Pex5p is coupled to the transport of newly synthesized peroxisomal proteins into the organelle matrix. However, direct evidence supporting this hypothesis was never provided. Here, using an in vitro peroxisomal import system, we show that insertion of Pex5p into the peroxisomal membrane requires the presence of cargo proteins. Strikingly the peroxisomal docking/translocation machinery is also able to catalyze the membrane insertion of a Pex5p truncated molecule lacking any known cargo-binding domain. These results suggest that the cytosol/peroxisomal cycle in which Pex5p is involved is directly or indirectly regulated by Pex5p itself and not by the peroxisomal docking/translocation machinery.
Gouveia
Alexandra M
AM
Instituto de Biologia Molecular e Celular, Rua do Campo Alegre, 823, 4150-180 Porto, Portugal.
Guimarães
Carla P
CP
Oliveira
Márcia E
ME
Sá-Miranda
Clara
C
Azevedo
Jorge E
JE
D000818:Animals; D007425:Intracellular Membranes / Q000737:chemistry / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000378:metabolism* / Q000648:ultrastructure; D011485:Protein Binding; D021381:Protein Transport; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D008565:Membrane Proteins; D000074435:Peroxisome-Targeting Signal 1 Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins