Fig. 1.

Homologous ribosomal proteins have highly diversified structure across the three domains of life. The diagram provides an overview of structural variability in 33 conserved proteins from 45 different species in the three domains of life. Each bar indicates the total number of amino acids in the 33 proteins in each species. The bars are colored to show the number of residues that form either the structurally invariable core (pink) or the variable protein segments (red). As the diagram shows, conserved ribosomal proteins carry nearly as many residues in structurally conserved protein segments as they carry in protein segments with distinct structure in different domains of life, suggesting a high degree of functional specialization of ribosomal proteins across the three domains of life.