Figure 2. The mass spectrum of intact ribosomes from T. thermophilus at a mass of 2.3 MDa, and with >50 different proteins and 3 large RNA molecules with masses of 2 325 463 ± 2000 Da and 798 165 ± 164 Da for the 70S and 30S, respectively.

The complex at 96 kDa is consistent with a heptameric stalk as opposed to the canonical pentameric stalks observed in all prokaryotic ribosomes up until this point. Subsequent X-ray analysis of L10 and its interactions with L12 confirmed this unexpected stoichiometry and enabled modelling of the 50S subunit with a heptameric stalk [25].