Putative E3 ubiquitin ligase involved in the rhizobial infection process. Plays an important role in the early steps of infection thread formation and in growth and differentiation of nodules. 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. Expressed in roots and nodules. By rhizobial infection. Promoter activity is detected at 3 days post-inoculation (dpi) in dividing cortical cells in roots and at 6 dpi in young emerging nodules. At 21 dpi strong promoter activity is detected in mature nodules in the nodule apices including the infection zone, with lower activity detected in the nitrogen-fixing zone.