SDHAF2 and cancer: While human SDHAF2 can complement Sdh5 in a Sdh5∆ yeast model, and heterozygous loss of function mutations in SDHAF2 are associated with hereditary paraganglioma (12), the complete loss of SDHAF2/SdhE in common human cancer-derived cell lines and thermophilic bacteria (13, 14) does not lead to the expected loss of SDHA flavination.