Figure 6. Actinonin, a naturally-occurring inhibitor of mitochondrial protein synthesis, blocks mammosphere formation.

Actinonin is a naturally-occurring antibiotic. However, actinonin also functions as an inhibitor of mitochondrial protein translation, by targeting a human mitochondrial protein, known as peptide deformylase (abbreviated as PDF). PDF is required to remove the formyl-group from the initiator methionine of mitochondrial proteins synthesized on mitochondrial ribosomes. Note that actinonin inhibited mammosphere formation, with an IC-50 between 25 and 50 μM. The bar graph shows the mean ± SEM, t-test, two-tailed test. ***p < 0.0001. N = 3 independent experiments.