Antoni Barrientos

Human mitochondrial ribosomes synthesize membrane proteins while docked at the inner membrane, but how insertion feeds back onto decoding has remained unclear. A recent study reveals that nascent-chain topology and early folding within the mitoribosomal vestibule modulate elongation speed, establishing kinetic checkpoints during respiratory chain biogenesis.

Abstract Translation elongation is a universally conserved step in protein synthesis, relying on elongation factors that engage the ribosomal L7/L12 stalk to mediate aminoacyl-tRNA delivery, accommodation, and ribosomal translocation. Using in organello cryo-electron microscopy, we reveal how the mitochondrial translation accelerator TACO1 promotes efficient elongation on human mitoribosomes.

Abstract The mitochondrial respiratory chain comprises four multimeric complexes (CI-CIV) that drive oxidative phosphorylation by transferring electrons to oxygen and generating the proton gradient required for ATP synthesis. These complexes can associate into supercomplexes (SCs), such as the CI + CIII₂ + CIV respirasome, but how SCs form, by joining preassembled complexes or by engaging partially assembled intermediates, remains unresolved.