MAF1 and obesity due to melanocortin 4 receptor deficiency: Since our data from S. cerevisiae cells partially contest the published data on mitochondrial metabolism in KO mice maf1+/−, we think it is worth reinspecting the metabolism using other, well-studied eukaryotic model organisms to answer the question of whether a lack of MAF1 protein correlates with dysfunction of mitochondrial metabolism and obesity or tumorigenesis.