E3 ubiquitin-protein ligase which accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates. Probably involved in the regulatory network controlling carbon source utilization. Ubiquitinates 'Lys-528' of the uric acid/xanthine transporter uapA at the cell membrane, leading to its internalization, sorting into the endosomal pathway to the vacuolar lumen where it is eventually degraded. 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. Protein modification; protein ubiquitination. Interacts with apyA and creD. Belongs to the RSP5/NEDD4 family.