Formation of irregular giant peroxisomes by overproduction of the crystalloid core protein methanol oxidase in the methylotrophic yeast Hansenula polymorpha.

AUTOR(ES)

Roggenkamp, R

RESUMO

The crystalloid core in peroxisomes of the methylotrophic yeast Hansenula polymorpha is composed of the octameric flavoprotein methanol oxidase (MOX). We transformed yeast cells with a high-copy-number vector harboring the cloned MOX gene in order to study the effects on regulation, protein import, and peroxisome biosynthesis. In transformed wild-type cells, no increase in expression of MOX was detectable. Mutants defective in MOX activity were isolated by a specific selection procedure. Two structural MOX mutants are described that allow overproduction of a fully active enzyme upon transformation at quantities of about two-thirds of the total cellular protein. The overproduced protein was imported into peroxisomes, altering their morphology (in thin sections) and stability in cell lysates; the organelles showed a tendency to form rectangular bodies, and their lumina were completely filled with the crystalloid structure. The overall size of the peroxisomes was increased severalfold in comparison with the size of nontransformed yeast cells. The results suggest high capacities of peroxisomal growth conferred by overproduction and import of a single protein.

Documentos Relacionados

• Cloning and characterization of the DAS gene encoding the major methanol assimilatory enzyme from the methylotrophic yeast Hansenula polymorpha.
• Molecular cloning and characterization of a gene coding for methanol oxidase in Hansenula polymorpha.
• Isolation and characterization of mutants impaired in the selective degradation of peroxisomes in the yeast Hansenula polymorpha.
• Peroxisomes in the methylotrophic yeast Hansenula polymorpha do not necessarily derive from pre-existing organelles.
• Architecture of peroxisomal alcohol oxidase crystals from the methylotrophic yeast Hansenula polymorpha as deduced by electron microscopy.