Peroxisomal targeting of PTS2 pre-import complexes in the yeast Saccharomyces cerevisiae.
Posttranslational matrix protein import into peroxisomes uses either one of the two peroxisomal targeting signals (PTS), PTS1 and PTS2. Unlike the PTS1 receptor Pex5p, the PTS2 receptor Pex7p is necessary but not sufficient to target cargo proteins into the peroxisomal matrix and requires coreceptors. Saccharomyces cerevisiae possesses two coreceptors, Pex18p and Pex21p, with a redundant but not a clearly defined function. To gain further insight into the early events of this import pathway, PTS2 pre-import complexes of S. cerevisiae were isolated and characterized by determination of size and protein composition in wild-type and different mutant strains. Mass spectrometric analysis of the cytosolic PTS2 pre-import complex indicates that Fox3p is the only abundant PTS2 protein under oleate growth conditions. Our data strongly suggest that the formation of the ternary cytosolic PTS2 pre-import complex occurs hierarchically. First, Pex7p recognizes cargo proteins through its PTS2 in the cytosol. In a second step, the coreceptor binds to this complex, and finally, this ternary 150 kDa pre-import complex docks at the peroxisomal membrane, where both the PTS1 and the PTS2 import pathways converge. Gel filtration analysis of membrane-bound subcomplexes suggests that Pex13p provides the initial binding partner at the peroxisomal membrane, whereas Pex14p assembles with Pex18p in high-molecular-weight complexes after or during dissociation of the PTS2 receptor.
Grunau
Silke
S
Institut für Physiologische Chemie, Ruhr-Universität Bochum, Universitätsstrasse 150, Bochum, Germany.
Schliebs
Wolfgang
W
Linnepe
Ruth
R
Neufeld
Christian
C
Cizmowski
Christian
C
Reinartz
Benedikt
B
Meyer
Helmut E
HE
Warscheid
Bettina
B
Girzalsky
Wolfgang
W
Erdmann
Ralf
R
D001692:Biological Transport / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins; D000074401:Peroxins; D000074437:Peroxisomal Targeting Signal 2 Receptor; D000074435:Peroxisome-Targeting Signal 1 Receptor; D020675:Peroxisomes / Q000378:metabolism*; D011485:Protein Binding; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C491105:PEX13 protein, S cerevisiae; C499195:PEX14 protein, S cerevisiae; C116845:PEX18 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