Plays an essential role in the assembly of succinate dehydrogenase (SDH), an enzyme complex (also referred to as respiratory complex II) that is a component of both the tricarboxylic acid (TCA) cycle and the mitochondrial electron transport chain, and which couples the oxidation of succinate to fumarate with the reduction of ubiquinone (coenzyme Q) to ubiquinol. Promotes maturation of the iron-sulfur protein subunit SDH2 of the SDH catalytic dimer, protecting it from the deleterious effects of oxidants. Acts together with SDHAF1 (SDH6). Interacts with SDH2 within an SDH1-SDH2 subcomplex. Present with 195 molecules/cell in log phase SD medium. Belongs to the complex I LYR family. SDHAF3 subfamily.