STED sheds insight on mitochondrial protein synthesis

Berlinguer-Palmini, Rolando

October 25, 2021

STED sheds insight on mitochondrial protein synthesis

Human mitochondrial DNA encodes 13 vital polypeptides that are components of the multisubunit complexes that couple Oxidative phosphorylation (OXPHOS) complexes that are found mainly in the invaginated cristae membranes. The inner boundary membrane (IBM) contains dynamic contact sites enriched for translocases that import proteins from the cytosol.

The majority of the OXPHOS subunits are nuclear-encoded and must therefore be imported from the cytosol through the outer membrane at contact sites with the inner boundary membrane.

As the majority of OXPHOS components are imported and need to be integrated in assembly with the mtDNA-encoded components, where does intramitochondrial translation occur?

As the mitochondrially encoded components are also integral members of these complexes, where does protein synthesis occur?

Image: Section of the human mitochondrial network taken at STED nanoscopy resolution. (See Figure 1 for more details).

In this paper the authors have adapted a click chemistry-based method coupled with stimulated emission depletion nanoscopy (STED) to address these questions reporting that, in human cells in culture, the majority of mitochondrial protein synthesis is detected at the cristae membranes and is spatially separated from the sites of RNA processing and maturation.