Oxa1l, the human homologue of the yeast Oxa1 protein, belongs to the evolutionarily conserved Oxa1/Alb3/YidC protein family [4]. It is an integral mitochondrial inner-membrane protein essential for the biogenesis of membrane proteins in mitochondria. Oxa1l is involved in pathways such as mitochondrial oxidative phosphorylation and is crucial for the cotranslational membrane insertion of mitochondrial-encoded proteins [1,2].

Mutations in Oxa1L in a patient led to severe encephalopathy, hypotonia, and developmental delay, along with complex IV deficiency in skeletal muscle [3]. Targeted depletion of Oxa1L in human cells or Drosophila melanogaster caused defects in the assembly of complexes I, IV, and V, indicating its role in the assembly of multiple respiratory chain complexes [3]. In HEK293 cells, stable short-hairpin (sh)RNA-mediated knockdown of Oxa1l resulted in decreased steady-state levels and activity of the F1Fo-ATP synthase and moderately reduced levels and activity of NADH:ubiquinone oxidoreductase (complex I) [4].

In conclusion, Oxa1l is essential for the correct biogenesis of multiple respiratory chain complexes and plays a key role in mitochondrial oxidative phosphorylation. Studies using gene-knockdown models in cells and Drosophila, as well as patient-derived mutations, have revealed its significance in mitochondrial-related diseases such as mitochondrial encephalopathy [3,4].