Electron microscopy investigation of the structure of cytoplasmic ribosomes of bean leaves

Electron microscopic observations on the large subunit of the rat liver ribosome

Active large subunits obtained by urea treatment of rat liver ribosomes, 59S, were compared with large subunits in intact ribosomes and with the 50S subunits obtained by EDTA treatment. For electron microscopy the specimens were negatively stained or shadow cast. The negatively stained 59S subunits had a slightly ovoidal form; their average dimensions, 244 +/- 17 x 207 +/- 18 A, were very close to the dimensions of the large subunits in intact ribosomes, and lay between the theoretical dimensions for anhydrous and fully hydrated particles that were calculated from the physical properties of the subunits in solution. The shadow-cast preparations showed particles of similar shape. The 50S subunits, which had lost their 5S RNA, were shadow cast at the same time. They appeared to be more spread out than the 59S subunits and had threadlike extensions. In the positively stained regions of uranyl oxalate-stained preparations the 50S particles varied greatly in shape and size, with average dimensions of 330 +/- 21 x 276 +/- 33 A, and showed threadlike extensions like those of the shadow-cast particles. For 50S particles in solution the frictional drag of these extensions probably accounts for their low sedimentation coefficient.

Induction of helical arrays of ribosomes by vinblastine sulfate in Escherichia coli

Physiological concentrations of vinblastine sulfate elicited ribosomal helices in large numbers in growing cultures of the osmotically sensitive mutant sud 24 and, after treatment with ethylenediaminetetraacetate, also in the K-12 strain. The helices were usually seen at the division plane and were often connected to the membrane. This method of induction of ribosomal helices offers a unique system for studying in vivo structure and function of the translational apparatus in relation to other cell components.