Metabolism of ribosomal proteins microinjected into the oocytes of Xenopus laevis
When the total proteins from Xenopus laevis 60 S ribosomal subunits (TP60) were /sup 3/H-labeled in vitro and injected back into X. laevis oocytes, most /sup 3/H-TP60 are integrated into the cytoplasmic 60 S subunits via the nucleus during 16 h of incubation. In the oocytes whose rRNA synthesis is inhibited, /sup 3/H-TP60 are rapidly degraded with a half-life of 2-3 h. This degradation ceased as soon as rRNA synthesis was resumed, suggesting that ribosomal proteins unassociated with nascent rRNA are unstable in the oocytes. The degradation of /sup 3/H-TP60 in the absence of RNA synthesis was inhibited by iodoacetamide, a cysteine protease inhibitor, resulting in the accumulation of /sup 3/H-TP60 in the nucleus reaching about a threefold concentration in the cytoplasm. Considering the results with enucleated oocytes, we suggest that the X. laevis nucleus has a limited capacity to accumulate ribosomal proteins in an active manner but that those ribosomal proteins accumulated in excess over rRNA synthesis are degraded by a cysteine protease in the nucleus. By contrast, ribosomal proteins from Escherichia coli only equilibrate between the nucleus and the cytoplasm and are degraded by serine protease(s) in the cytoplasm without being integrated in the form of ribosomes in the nucleus.
- Research Organization:
- Yamanashi Medical College, Japan
- OSTI ID:
- 5600611
- Journal Information:
- Exp. Cell Res.; (United States), Vol. 174:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
PROTEINS
METABOLISM
RIBOSOMAL RNA
BIOSYNTHESIS
BIOLOGICAL HALF-LIFE
BOROHYDRIDES
CELL NUCLEI
CYTOPLASM
ENZYME INHIBITORS
ESCHERICHIA COLI
FROGS
INHIBITION
OOCYTES
SERINE PROTEINASES
TRACER TECHNIQUES
TRITIUM COMPOUNDS
URIDINE
AMPHIBIANS
ANIMALS
AQUATIC ORGANISMS
AZINES
BACTERIA
BORON COMPOUNDS
CELL CONSTITUENTS
ENZYMES
GERM CELLS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROLASES
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MICROORGANISMS
NUCLEIC ACIDS
NUCLEOSIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PEPTIDE HYDROLASES
PYRIMIDINES
RIBOSIDES
RNA
SYNTHESIS
URACILS
VERTEBRATES
550501* - Metabolism- Tracer Techniques