This domain is found in alkyl sulfatases such as the Pseudomonas aeruginosa SDS hydrolase (Swiss:Q9I5I9), where it acts as a dimerisation domain [1]

1: The crystal structure of SdsA1, an alkylsulfatase from Pseudomonas aeruginosa, defines a third class of sulfatases. Hagelueken G, Adams TM, Wiehlmann L, Widow U, Kolmar H, Tummler B, Heinz DW, Schubert WD; Proc Natl Acad Sci U S A. 2006;103:7631-7636. PMID:16684886