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The Hansenula polymorpha PER8 gene encodes a novel peroxisomal integral membrane protein involved in proliferation
X Tan1, H R Waterham, M Veenhuis
1Department of Chemistry, Biochemistry, and Molecular Biology, Oregon Graduate Institute of Science & Technology, Portland 97291-1000.
Abstract:
We previously described the isolation of mutants of the methylotrophic yeast Hansenula polymorpha that are defective in peroxisome biogenesis. Here, we describe the characterization of one of these mutants, per8, and the cloning of the PER8 gene. In either methanol or methylamine medium, conditions that normally induce the organelles, per8 cells contain no peroxisome-like structures and peroxisomal enzymes are located in the cytosol. The sequence of PER8 predicts that its product (Per8p) is a novel polypeptide of 34 kD, and antibodies against Per8p recognize a protein of 31 kD. Analysis of the primary sequence of Per8p revealed a 39-amino-acid cysteine-rich segment with similarity to the C3HC4 family of zinc-finger motifs. Overexpression of PER8 results in a markedly enhanced increase in peroxisome numbers. We show that Per8p is an integral membrane protein of the peroxisome and that it is concentrated in the membranes of newly formed organelles. We propose that Per8p is a component of the molecular machinery that controls the proliferation of this organelle.
Insights
The PER8 gene is crucial for peroxisome biogenesis in Hansenula polymorpha yeast. Its protein product, Per8p, is an integral membrane protein essential for organelle proliferation.
Area of Science:
- Cell Biology
- Molecular Biology
- Yeast Genetics
Background:
- Peroxisome biogenesis is essential for cellular function in methylotrophic yeasts.
- Mutants defective in peroxisome biogenesis provide insights into organelle formation.
- Hansenula polymorpha is a model organism for studying peroxisome development.
Purpose of the Study:
- To characterize the per8 mutant of Hansenula polymorpha.
- To clone and identify the PER8 gene responsible for peroxisome biogenesis.
- To elucidate the function and localization of the Per8 protein (Per8p).
Main Methods:
- Genetic analysis of the per8 mutant.
- Gene cloning and sequencing of PER8.
- Protein expression analysis using antibodies against Per8p.
- Subcellular localization studies of Per8p.
Main Results:
- The per8 mutant lacks peroxisomes and exhibits cytosolic localization of peroxisomal enzymes.
- The PER8 gene encodes a novel 34 kD polypeptide (Per8p) with a zinc-finger motif.
- Per8p is an integral membrane protein concentrated in newly formed peroxisomes.
- Overexpression of PER8 leads to increased peroxisome numbers.
Conclusions:
- Per8p is a key component of the peroxisome biogenesis machinery.
- Per8p plays a critical role in regulating peroxisome proliferation.
- The findings contribute to understanding the molecular mechanisms of organelle formation.