A pan-eukaryotic analysis of mitochondrial ribosomes uncovers major evolutionary transitions

Mitochondrial ribosomes, or mitoribosomes, have undergone significant divergence from their bacterial origins and across various eukaryotic organisms. Despite numerous general trends identified, the specific aspects of their evolution remain elusive. To gain a better understanding, researchers examined sequences from 85 distinct eukaryotes to map the protein composition throughout the evolution of mitochondrial translation.

Their findings indicate that the Last Eukaryotic Common Ancestor (LECA) mitoribosomal proteome contained nearly the entire bacterial protein complement, with at least 23 proteins added post the -proteobacterial endosymbiosis event. The subsequent evolution post-LECA involved extensive but lineage-specific remodeling of these proteins.

Additionally, the study uncovers previously unknown homologies among several mitoribosomal proteins, leading to a unified and updated mitoribosomal nomenclature. The data also suggests protein retargeting between organellar ribosomes, demonstrating remarkable intercompartmental structural compatibility. These discoveries underscore the remarkable evolutionary adaptability of mitoribosomes and provide a comprehensive reference framework for future research in the field.