Core component of the CTLH E3 ubiquitin-protein ligase complex that selectively accepts ubiquitin from UBE2H and mediates ubiquitination and subsequent proteasomal degradation of the transcription factor HBP1. MAEA and RMND5A are both required for catalytic activity of the CTLH E3 ubiquitin-protein ligase complex (PubMed:29911972). Catalytic activity of the complex is required for normal cell proliferation (PubMed:29911972). The CTLH E3 ubiquitin-protein ligase complex is not required for the degradation of enzymes involved in gluconeogenesis, such as FBP1 (PubMed:29911972). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Identified in the CTLH complex that contains GID4, RANBP9 and/or RANBP10, MKLN1, MAEA, RMND5A (or alternatively its paralog RMND5B), GID8, ARMC8, WDR26 and YPEL5 (PubMed:29911972). Within this complex, MAEA, RMND5A (or alternatively its paralog RMND5B), GID8, WDR26, and RANBP9 and/or RANBP10 form the catalytic core, while GID4, MKLN1, ARMC8 and YPEL5 have ancillary roles (PubMed:29911972).