Members of this family adopt a structure consisting of three alpha helices, in an immunoglobulin/albumin-binding domain-like fold. They are predominantly found in the enzyme alpha-mannosidase [1].

1: The structure of bovine lysosomal alpha-mannosidase suggests a novel mechanism for low-pH activation. Heikinheimo P, Helland R, Leiros HK, Leiros I, Karlsen S, Evjen G, Ravelli R, Schoehn G, Ruigrok R, Tollersrud OK, McSweeney S, Hough E; J Mol Biol. 2003;327:631-644. PMID:12634058