This domain is found in the E. coli Type III secretion effector proteins SopA and NleL [1,2]. These proteins have been shown to act as E3 ubiquitin ligase enzymes. This domain contains the active site cysteine residue.

1: Biochemical and structural studies of a HECT-like ubiquitin ligase from Escherichia coli O157:H7. Lin DY, Diao J, Zhou D, Chen J; J Biol Chem. 2011;286:441-449. PMID:20980253

2: Crystal structure of SopA, a Salmonella effector protein mimicking a eukaryotic ubiquitin ligase. Diao J, Zhang Y, Huibregtse JM, Zhou D, Chen J; Nat Struct Mol Biol. 2008;15:65-70. PMID:18066077