Members of this family are found in 3-mercaptopyruvate sulfurtransferase, and have no known function. They adopt a structure consisting of a four-stranded antiparallel beta-sheet and an alpha-helix, arranged in a beta(2)-alpha-beta(2) fashion, and bearing a remarkable structural similarity to the FK506-binding protein class of peptidylprolyl cis/trans-isomerase [1].

1: The crystal structure of Leishmania major 3-mercaptopyruvate sulfurtransferase. A three-domain architecture with a serine protease-like triad at the active site. Alphey MS, Williams RA, Mottram JC, Coombs GH, Hunter WN; J Biol Chem. 2003;278:48219-48227. PMID:12952945