title: Yeast Pex14p possesses two functionally distinct Pex5p and one Pex7p binding sites.
abstract: Current evidence favors a cycling receptor model for the import of peroxisomal matrix proteins. The yeast Pex14 protein together with Pex13p and Pex17p form the docking subcomplex at the peroxisomal membrane and interact in this cycle with both soluble import receptors Pex5p and Pex7p. In a first step of a structure-function analysis of Saccharomyces cerevisiae Pex14p, we mapped its binding sites with both receptors. Using the yeast two-hybrid system and pull-down assays, we showed that Pex5p directly interacts with two separate regions of ScPex14p, amino acid residues 1-58 and 235-308. The latter binding site at the C terminus of ScPex14p overlaps with a binding site of Pex7p at amino acid residues 235-325. The functional assessment of these two binding sites of ScPex14p with the peroxisomal targeting signal receptors indicates that they have distinct roles. Deletion of the N-terminal 58 amino acids caused a partial defect of matrix protein import in pex14delta cells expressing the Pex14-(59-341)-p fragment; however, it did not lead to a pex phenotype. In contrast, truncation of the C-terminal 106 amino acids of ScPex14p completely blocked this process. On the basis of these and other published data, we propose that the C terminus of Pex14p contains the actual docking site and discuss the possibility that the N terminus could be involved in a Pex5p-Pex14p association inside the peroxisomal membrane.
authors.affiliation: Institut für Physiologische Chemie, Abteilung für Systembiochemie, Medizinische Fakultät der Ruhr-Universität Bochum, 44780 Bochum, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Niederhoff
authors.forename: Nadja M
authors.initials: NM
authors.lastname: Meindl-Beinker
authors.forename: Daniela
authors.initials: D
authors.lastname: Kerssen
authors.forename: Uta
authors.initials: U
authors.lastname: Perband
authors.forename: Antje
authors.initials: A
authors.lastname: Schäfer
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schliebs
authors.forename: Wolf-H
authors.initials: WH
authors.lastname: Kunau
mesh_terms: D001665:Binding Sites; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D017353:Gene Deletion; D008565:Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000502:physiology*; D000074401:Peroxins; D000074437:Peroxisomal Targeting Signal 2 Receptor; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000737:chemistry / Q000378:metabolism; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000502:physiology*; D012097:Repressor Proteins / Q000737:chemistry / Q000502:physiology*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000502:physiology*; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D013347:Subcellular Fractions / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C499195:PEX14 protein, S cerevisiae; C499509:PEX5 protein, S cerevisiae; C082902:PEX7 protein, S cerevisiae; D000074401:Peroxins; D000074437:Peroxisomal Targeting Signal 2 Receptor; D000074435:Peroxisome-Targeting Signal 1 Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D001616:beta-Galactosidase