Structure of the 80S ribosome from Saccharomyces cerevisiae - tRNA-ribosome and subunit-subunit interactions

A cryo-EM reconstruction of the translating yeast 80S ribosome was analyzed . Computationally separated rRNA and protein densities were used for dockin g of appropriately modified rRNA models and homology models of yeast riboso mal proteins. The core of the ribosome shows a remarkable degree of conserv ation. However, some significant differences in functionally important regi ons and dramatic changes in the periphery due to expansion segments and add itional ribosomal proteins are evident. As in the bacterial ribosome, bridg es between the subunits are mainly formed by RNA contacts. Four new bridges are present at the periphery. The position of the P site tRNA coincides pr ecisely with its prokaryotic counterpart, with mainly rRNA contributing to its molecular environment. This analysis presents an exhaustive inventory o f an eukaryotic ribosome at the molecular level.