Li, G.-W. et al. Cell 157, 624–635 (2014).

Dividing cells expend a great deal of energy in protein synthesis, making it important to understand how the dynamics of the process have been optimized by evolution. Li et al. used ribosomal profiling to make absolute measurements of synthesis rates for more than 96% of cellular proteins produced by Escherichia coli. The method consists of digesting RNA and sequencing the fragments that are protected by bound ribosomes; protein synthesis rates can be derived from the density of bound ribosomes. Using the approach, the researchers found that steady-state levels of stable proteins are controlled to a large extent at the level of protein synthesis rather than degradation. The analysis revealed many cases of optimized translation in the bacterium. For example, individual components of protein complexes are synthesized in stoichiometric ratios.