Pex17p-dependent assembly of Pex14p/Dyn2p-subcomplexes of the peroxisomal protein import machinery

Abstract

Peroxisomal matrix protein import is facilitated by cycling receptors that recognize their cargo proteins in the cytosol by peroxisomal targeting sequences (PTS). In the following, the assembled receptor-cargo complex is targeted to the peroxisomal membrane where it docks to the docking-complex as part of the peroxisomal translocation machinery. The docking-complex is composed of Pex13p, Pex14p and in yeast also Pex17p, whose function is still elusive. In order to characterize the function of Pex17p, we compared the composition and size of peroxisomal receptor-docking complexes from wild-type and pex17Δ cells. Our data demonstrate that the deficiency of Pex17p affects the stoichiometry of the constituents of an isolated 600kDa complex and that pex17Δ cells lack a high molecular weight complex (>900kDa) of unknown function. We identified the dynein light chain protein Dyn2p as an additional core component of the Pex14p/Pex17p-complex. Both, Pex14p and Pex17p interact directly with Dyn2p, but in vivo, Pex17p turned out to be prerequisite for an association of Dyn2p with Pex14p. Finally, like pex17Δ also dyn2Δ cells lack the high molecular weight complex. As dyn2Δ cells also display reduced peroxisomal function, our data indicate that Dyn2p-dependent formation of the high molecular weight Pex14p-complex is required to maintain peroxisomal function on wild-type level.