title: Hansenula polymorpha Pex3p is a peripheral component of the peroxisomal membrane.
abstract: Hansenula polymorpha Pex3p plays an essential role in the biogenesis and maintenance of the peroxisomal membrane. In the initial report, bakers' yeast Pex3p was suggested to represent an integral component of the peroxisomal membrane, containing one membrane-spanning region that exposes the N terminus of the protein into the organellar matrix. Biochemically, HpPex3p behaved like an integral membrane protein as it was resistant toward high salt and carbonate treatment. However, urea fully removed Pex3p from the membrane under conditions in which the integral membrane protein Pex10p was resistant to this treatment. Additional experiments, including protease protection assays and pre-embedding labeling experiments on purified organellar fractions from cells that produced Pex3ps carrying Myc epitopes at various selected locations in the protein, revealed that invariably all Myc tags were accessible for externally added proteases and antibodies, independent of the presence of detergents. Also, overproduction of Pex3p failed to demonstrate the typical integral membrane protein structures in fracture faces of freeze-fractured peroxisomes. Taken together, our data suggest that HpPex3p does not span the peroxisomal membrane but instead is tightly associated to the cytosolic face of the organelle where it may be present in focal protein clusters.
authors: Eukaryotic Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, P. O. Box 14, 9750 AA Haren, The Netherlands.
authors: Gert Jan
authors: GJ
authors: Haan
authors: Klaas Nico
authors: KN
authors: Faber
authors: Richard J S
authors: RJ
authors: Baerends
authors: Anne
authors: A
authors: Koek
authors: Arjen
authors: A
authors: Krikken
authors: Jan A K W
authors: JA
authors: Kiel
authors: Ida J
authors: IJ
authors: van der Klei
authors: Marten
authors: M
authors: Veenhuis
mesh_terms: D018528:ATP-Binding Cassette Transporters; D001483:Base Sequence; D005656:Fungal Proteins / Q000737:chemistry*; D007425:Intracellular Membranes / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry*; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D000074401:Peroxins; D020675:Peroxisomes / Q000737:chemistry*; D010843:Pichia / Q000648:ultrastructure*; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D018528:ATP-Binding Cassette Transporters; D005656:Fungal Proteins; D008565:Membrane Proteins; C070895:PEX3 protein, S cerevisiae; D000074401:Peroxins; C406793:SPF1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins