Genetic studies have linked the evolutionary novel, anthropoid primate-specific gene locus G72/G30 in the etiology of schizophrenia and other psychiatric disorders. However, the function of the protein encoded by this locus, LG72, is currently controversially discussed. Some studies have suggested that LG72 binds to and regulates the activity of the peroxisomal enzyme D-amino-acid-oxidase, while others proposed an alternative role of this protein due to its mitochondrial location in vitro. Studies with transgenic mice expressing LG72 further suggested that high levels of LG72 lead to an impairment of mitochondrial functions with a concomitant increase in reactive oxygen species production. In the present study, we now performed extensive interaction analyses and identified the mitochondrial methionine-R-sulfoxide reductase B2 (MSRB2) as a specific interaction partner of LG72. MSRB2 belongs to the MSR protein family and functions in mitochondrial oxidative stress defense. Based on our results, we propose that LG72 is involved in the regulation of mitochondrial oxidative stress.