Messenger ribonucleoprotein particles in unfertilized sea urchin eggs

John F. Kaumeyer, Nancy A. Jenkins, Rudolf A. Raff

Research output: Contribution to journalArticle

39 Scopus citations

Abstract

The properties of poly(A)-containing messenger ribonucleoprotein particles (mRNPs) from unfertilized sea urchin eggs isolated under various ionic conditions were studied. Poly(A)-containing RNPs of eggs sediment with a modal value of 60-65 S under all conditions used. However, buoyant densities vary strikingly with conditions of particle preparation. Deproteinized poly(A)-containing mRNA has an average molecular weight of about 1 × 106. RNPs prepared in 0.35 M Na+ in the absence of Mg2+ contain an average of 0.25 × 106 daltons of protein, while particles prepared in 0.05 M Na+ in the absence of Mg2+ contain 0.35 to 11 × 106 daltons of protein per RNA molecule. Particles prepared in 0.35 M Na+ plus 5 mM Mg2+ contain 1.4 × 106 daltons of protein suggesting that Mg2+ may be necessary for maintenance of RNP intergrity if high Na+ concentrations are used to prevent nonspecific RNA-protein interactions. Particles prepared in 0.35 M K+ contain 0.9 × 106 daltons of protein in both Mg2+ and EDTA. Mg2+ does not cause significant aggregation of particles, since the size of RNA extracted from RNPs is proportional to RNP sedimentation rate. Monovalent cation concentrations normally used in analysis of RNPs by sedimentation cause deproteinized poly(A)-containing RNA to sediment with abnormally high sedimentation coefficients, indicating that high sedimentation rates alone do not indicate that RNA is contained in an RNP.

Original languageEnglish (US)
Pages (from-to)266-278
Number of pages13
JournalDevelopmental Biology
Volume63
Issue number2
DOIs
StatePublished - Jan 1 1978

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

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