Ribosome stoichiometry: from form to function.

The existence of eukaryotic ribosomes with distinct ribosomal protein (RP) stoichiometry and regulatory roles in protein synthesis been speculated for over sixty years. Recent advances in mass spectrometry and high throughput analysis have begun to identify and characterize distinct ribosome stoichiometry in yeast or mammalian systems. In addition to RP stoichiometry, ribosomes play host to a vast array of protein modifications, effectively expanding the number of human RPs from 80 to many thousands of distinct proteoforms. Is it possible these proteoforms combine to function as a ‘ribosome code’ to tune protein synthesis? We outline the specific benefits that translational regulation by specialized ribosomes can offer and discuss the means and methodologies available to correlate and characterize RP stoichiometry with function. We highlight previous research with a focus on formulating hypotheses that can guide future experiments and crack the ‘ribosome code’.