Pichia pastoris Pex14p, a phosphorylated peroxisomal membrane protein, is part of a PTS-receptor docking complex and interacts with many peroxins

The peroxisomal protein import machinery plays a central role in the assemb ly of this organelle in all eukaryotes, Genes encoding components of this m achinery, termed peroxins or Pex proteins, have been isolated and character ized in several yeast species and in mammals, including humans. Here me rep ort on one of these components, Pex14p, from the methylotrophic yeast Pichi a pastoris. Work in other organisms has shown that Pex14p is located on the cytoplasmic surface of the peroxisomal membrane and binds peroxisomal targ eting signal (PTS) receptors carrying proteins bound for the peroxisomal ma trix, results that have led to the hypothesis that Pex14p is a receptor-doc king protein. P. pastoris Pex14p (PpPex14p) behaves like an integral membra ne protein, with its C-terminus exposed on the cytosolic side of the peroxi somal membrane. PpPex14p complexes with many peroxins, including Pex3p (Sny der et al,, 1999b), Pex5p, Pex7p, Pex13p, Pex17p, itself, and a previously unreported peroxin, Pex8p, A portion of Pex14p is phosphorylated, but both phosphorylated and unphosphorylated forms of Pex14p interact with several p eroxins, The interactions between Pex14p and other peroxins provide clues r egarding the function of Pex14p in peroxisomal protein import. Copyright (C ) 2001 John Wiley & Sons, Ltd.