Required for O-acetylhomoserine sulfhydrylase (OAHS)-independent homocysteine (Hcy) biosynthesis (PubMed:25315403, PubMed:25938369). Together with MA_1821, catalyzes the condensation of sulfide with aspartate semialdehyde to generate homocysteine. May be involved in the reduction of the disulfide formed in MA_1821 (Probable). Binds 2 [4Fe-4S] cluster. Amino-acid biosynthesis. May form a complex with MA_1821.