Three-dimensional structure of the mammalian cytoplasmic ribosome.
A three-dimensional reconstruction of the 80 S ribosome from rabbit reticulocytes has been calculated from low-dose electron micrographs of a negatively stained single-particle specimen. At 37 A resolution, the precise orientations of the 40 S and 60 S subunits within the monosome can be discerned. The translational domain centered on the upper portion of the subunit/subunit interface is quite open, allowing considerable space between the subunits for interactions with the non-ribosomal macromolecules involved in protein synthesis. Further, the cytosolic side of the monosome is strikingly more open than the membrane-attachment side, suggesting a greater ease of communication with the cytoplasm, which would facilitate the inwards and outwards diffusion of a number of ligands. Although the 60 S subunit portion of the 80 S structure shows essentially all of the major morphological features identified for the eubacterial 50 S large subunit, it appears to possess a region of additional mass that evidently accounts for the more ellipsoidal form of the eukaryotic subunit.
Verschoor
A
A
Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509.
Frank
J
J
D000818:Animals; D003593:Cytoplasm / Q000648:ultrastructure; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D014176:Protein Biosynthesis; D011817:Rabbits; D012270:Ribosomes / Q000648:ultrastructure*