Biogenesis of Glyoxysomes

Zimmermann, Richard und Neupert, Walter (November 1980): Biogenesis of Glyoxysomes. Synthesis and Intracellular Transfer of Isocitrate Lyase. In: European Journal of Biochemistry, Bd. 112, Nr. 2: S. 225-233

Abstract

Biosynthesis of isocitrate lyase, a tetrameric enzyme of the glyoxysomal matrix, was studied in Neurospora crassa, in which the formation of glyoxysomes was induced by a substitution of sucrose medium by acetate medium.

* 1.

Translation of Neurospora mRNA in reticulocyte lysates yields a product which has the same apparent molecular weight as the subunit of the functional enzyme. Using N-formyl[35S]methionyl tRNAMetf as a label, the translation product shows the same apparent size which indicates that the amino terminus has no additional 'signal'-type sequence. * 2.

Read-out systems employing free and membrane-bound polysomes show that only free ribosomes are active in the synthesis of isocitrate lyase. * 3.

Isocitrate lyase synthesized in reticulocyte lysate is released into the supernatant and is soluble in a monomeric form. It interacts with Triton X-100 to form mixed micells in contrast to the functional tetrameric form. * 4.

Transfer of isocitrate lyase synthesized in vitro into isolated glyoxysomes is suggested by results of experiments in which supernatants from reticulocyte lysates are incubated with a particle fraction isolated from acetate-grown cells. No transfer occurs when particles from non-induced cells are employed. Resistance to added proteinase is used as a criterion for transmembrane transfer.

The data support a post-translational transfer mechanism for isocitrate lyase. They suggest that isocitrate lyase passes through a cytosolic precurscr pool as a monomer and is transferred into glyoxysomes.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Medizin
• Themengebiete: 600 Technik, Medizin, angewandte Wissenschaften > 610 Medizin und Gesundheit
• ISSN: 1432-1033