Visualizing ribosome biogenesis: parallel assembly pathways for the 30S subunit.

The bacterial ribosome is made up of two subunits (50 S and 30 S ) that together comprise 55 proteins and three large ribosomal RNAs. Both subunits self-assemble from their components in vitro, and hence, Mulder et al. (p. [673][1]) were able to use a derivation of time-resolved electron microscopy to monitor assembly of the 30 S subunit. This approach identified 14 distinct assembly intermediates and allowed characterization of the population, conformation, and protein composition of the intermediates along the assembly pathway. [1]: /lookup/doi/10.1126/science.1193220