E3 ubiquitin-protein ligase required for aquaporin levels regulation. 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 Arabidopsis PIP2-1. Localization experiments made in a heterologous system. By drought, cold, high salt, wounding and ethylene. Not induced by abscisic acid. The RING-type zinc finger domain is required for E3 ligase activity.