INVOLVEMENT OF A NOVEL RIBOSOME ASSOCIATED FACTOR INTRANSLATION REGULATION

Ribosome inactivation is a vital adaptive mechanism that allows the cells to conserve resources under stress by controlling protein synthesis1–3. Although ribosome-interacting proteins in facilitating ribosome dimerization and hibernation are well studied in bacteria and eukaryotes4–8, similar mechanisms in archaea remain poorly understood. Here we present high-resolution cryo-electron microscopy structures of an archaeal 30S ribosomal dimer stabilized by a ribosome dimerization factor (aRDF) from Pyrococcus furiosus. Structures were resolved at 3.2 Å with a unique head-to-body architecture of the 30S ribosomal subunits, distinct from the dimerized ribosome structures observed in other domains of life. The aRDF protein interacts directly with the eS32 ribosomal protein, a key player in subunit association. Therefore, based on biochemical and structural evidence aRDF ́s function is to halt the assembly of functional 70S ribosomes. These findings provide novel insights into ribosome inactivation mechanisms in archaea presenting aRDF as an archaeal ribosome anti-association factor that inhibits ribosome subunit joining for translational control purposes (Scheme 1).