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Peroxisomal membrane protein import does not require Pex17p
Courtney C Harper1, Sarah T South, J Michael McCaffery
1Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Abstract:
Of the approximately 20 proteins required for peroxisome biogenesis, only four have been implicated in the process of peroxisomal membrane protein (PMP) import: Pex3p, Pex16p, Pex17p, and Pex19p. To improve our understanding of the role that Pex17p plays in PMP import, we examined the behavior of PMPs in a Pichia pastoris pex17 mutant. Relative to wild-type cells, pex17 cells appeared to have a mild reduction in PMP stability and slightly aberrant PMP behavior in subcellular fractionation experiments. However, we also found that the behavior of PMPs in the pex17 mutant was indistinguishable from PMP behavior in a pex5 mutant, which has no defect in PMP import, and was far different from PMP behavior in a pex3 mutant, which has a bona fide defect in PMP import. Furthermore, we found that a pex14 mutant, which has no defect in PMP import, lacks detectable levels of Pex17p. Based on these and other results, we propose that Pex17p acts primarily in the matrix protein import pathway and does not play an important role in PMP import.
Insights
Pichia pastoris Pex17p does not play a significant role in peroxisomal membrane protein (PMP) import. Studies suggest Pex17p primarily functions in the matrix protein import pathway, not PMP import.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Peroxisome biogenesis requires approximately 20 proteins.
- Only four proteins (Pex3p, Pex16p, Pex17p, Pex19p) are implicated in peroxisomal membrane protein (PMP) import.
- The precise role of Pex17p in PMP import remains unclear.
Purpose of the Study:
- To investigate the function of Pex17p in PMP import.
- To elucidate the role of Pex17p in peroxisome biogenesis.
Main Methods:
- Analysis of Pichia pastoris pex17 mutant cells.
- Subcellular fractionation experiments.
- Comparison of PMP behavior in pex17, pex5, pex3, and pex14 mutants.
Main Results:
- Pex17 mutant cells showed mild PMP instability and aberrant PMP behavior.
- PMP behavior in pex17 mutants was similar to pex5 mutants (no PMP import defect).
- PMP behavior in pex17 mutants differed significantly from pex3 mutants (PMP import defect).
- Pex14 mutants (no PMP import defect) lacked detectable Pex17p.
Conclusions:
- Pex17p's primary role is likely in matrix protein import, not PMP import.
- Pex17p does not appear essential for PMP import.
- Pex17p's function is distinct from proteins directly involved in PMP import.