This NEL or novel E3 ligase domain is found at the C-terminus of bacterial virulence factors. Its sequence is different from those of the eukaryotic HECT and RING-finger E3 ligases, and it subverts the host ubiquitination process. At the N-terminus of the family-members there is a series of LRR repeats, and the NEL domain interacts with the most N-terminal repeat. The key residue for the ligation step is the cysteine, eg found at position 386 in UniProtKB:E7K2H2. The LRR section sequesters this active site until invasion has occurred [1].

1: A family of Salmonella virulence factors functions as a distinct class of autoregulated E3 ubiquitin ligases. Quezada CM, Hicks SW, Galan JE, Stebbins CE; Proc Natl Acad Sci U S A. 2009;106:4864-4869. PMID:19273841