Comparison of Artemia salina and Escherichia coli ribosome structure by electron microscopy

The structure of eukaryotic Artemia salina and prokaryotic Escherichia coli ribosomes has been compared by electron microscopy. Despite the established differences in size and in the amount and proportion of the protein and RNA moieties, both types of ribosomes appear to have substantial similarity in the overall shape and in the mutual orientation of the subunits on the monosome. The small subunit is located in the "crown" region of the large subunit lengthwise between the two side crests. However, high-resolution electron microscopy reveals distinct differences in the fine structure of both small and large subunits. The 40S A. salina subunit with three structural domains is more complex than the corresponding E. coli subunit. The 60S A. salina subunit has a less expressed "crown" region and shows a knob-like protrusion in the base. Structural asymmetry is a characteristic feature common to subunits and monosomes from both A. salina and E. coli.