Nucleocytoplasmic transport of ribosomes in a eukaryotic system: Is there a facilitated transport process

Journal Article · Wed Mar 01 00:00:00 EST 1989 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.86.6.1791· OSTI ID:7068655

Khanna-Gupta, A; Ware, V C ^[1]

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1. Lehigh Univ., Bethlehem, PA (USA)

The authors have examined the kinetics of the process by which ribosomes are exported from the nucleus to the cytoplasm using Xenopus laevis oocytes microinjected into the germinal vesicle with radiolabeled ribosomes or ribosomal subunits from X. laevis, Tetrahymena thermophila, or Escherichia coli. Microinjected eukaryotic mature ribosomes are redistributed into the oocyte cytoplasm by an apparent carrier-mediated transport process that exhibits saturation kinetics as increasing amounts of ribosomes are injected. T. thermophila ribosomes are competent to traverse the Xenopus nuclear envelope, suggesting that the basic mechanism underlying ribosome transport is evolutionarily conserved. Microinjected E. coli ribosomes are not transported in this system, indicating that prokaryotic ribosomes lack the signals required for transport. Surprisingly, coinjected small (40S) and large (60S) subunits from T. thermophila are transported significantly faster than individual subunits. These observations support a facilitated transport model for the translocation of ribosomal subunits as separate units across the nuclear envelope whereby the transport rate of 60S or 40S subunits is enhanced by the presence of the partner subunit. Although the basic features of the transport mechanism have been preserved through evolution, other aspects of the process may be mediated through species-specific interactions. They hypothesize that a species-specific nuclear 40S-60S subunit association may expedite the transport of individual subunits across the nuclear envelope.

• OSTI ID: 7068655
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Vol. 86:6; ISSN 0027-8424
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
MEMBRANE TRANSPORT
BIOCHEMICAL REACTION KINETICS
RIBOSOMES
SUBCELLULAR DISTRIBUTION
AMPHIBIANS
BIOLOGICAL EVOLUTION
ESCHERICHIA COLI
LABELLED COMPOUNDS
NUCLEOPROTEINS
OOCYTES
PHOSPHORUS 32
RIBOSOMAL RNA
TETRAHYMENA
TRITIUM COMPOUNDS
URIDINE
ANIMALS
AQUATIC ORGANISMS
AZINES
BACTERIA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CELL CONSTITUENTS
CILIATA
DAYS LIVING RADIOISOTOPES
DISTRIBUTION
GERM CELLS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INVERTEBRATES
ISOTOPES
KINETICS
LIGHT NUCLEI
MICROORGANISMS
NUCLEI
NUCLEIC ACIDS
NUCLEOSIDES
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOIDS
PHOSPHORUS ISOTOPES
PROTEINS
PROTOZOA
PYRIMIDINES
RADIOISOTOPES
REACTION KINETICS
RIBOSIDES
RNA
URACILS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques