Affordable Access

Publisher Website

Comparative studies on mitochondrial and cytoplasmic ribosomes ofTetrahymena pyriformis

Journal of Molecular Biology
Publication Date
DOI: 10.1016/0022-2836(70)90082-3
  • Biology
  • Chemistry


Abstract Physico-chemical properties of Tetrahymena mitochondrial and cytoplasmic ribosomes and their components, rRNA † † Abbreviation used: rRNA, ribosomal RNA, either mitochondrial or cytoplasmic. and proteins were investigated. The mitochondrial and cytoplasmic ribosomes were 80 s and indistinguishable in sedimentation analysis at 10 −2 m-Mg 2+. However, these ribosomes exhibit different sensitivity to Mg 2+ concentrations. The cytoplasmic ribosomes consist of 60 and 40 s subunits, while the mitochondrial ribosomes produced only one sedimenting species 55 s in low Mg 2+- or EDTA-containing buffer. Buoyant densities of mitochondrial and cytoplasmic 80 s ribosomes and respective subunits after formaldehyde fixation showed reproducible differences. Mitochondrial 80 s showed a density 1.46 g/cm 3, and two density species, I = 1.52 g/cm 3 and II = 1.46 g/cm 3 were obtained in a ratio of 1:2 in amount from the 55 s subunit, while the cytoplasmic 80 s ribosomes had a density 1.56 g/cm 3 and their subunits 60 and 40 s had densities 1.57 and 1.53 g/cm 3, respectively. Electrophoretic differences exist between proteins isolated from mitochondrial and cytoplasmic 80 s ribosomes in polyacrylamide gel columns. Mitochondrial and cytoplasmic rRNA's isolated from their respective 80 s ribosomes were 21 and 14 s, and 26 and 17 s, respectively. 5 and 4 s RNA's were also present. Base compositions of mitochondrial and cytoplasmic rRNA's were different. Furthermore, the 21 and 14 s mitochondrial rRNA's were complementary to 3.8 and 1.9% of the mitochondrial DNA, respectively. No significant complementarity exists between mitochondrial DNA and cytoplasmic rRNA's. These results established that Tetrahymena mitochondria contain unique ribosomes separate from the cytoplasmic ribosomes.

There are no comments yet on this publication. Be the first to share your thoughts.