This domain is found at the N-terminal of the uncharacterised Lem10 protein from Legionella pneumophila [1]. This has an alpha-helical bundle and a central five stranded beta-sheet that form a 2-layer sandwich.

1: Crystal structure of the Legionella pneumophila Lem10 effector reveals a new member of the HD protein superfamily. Morar M, Evdokimova E, Chang C, Ensminger AW, Savchenko A; Proteins. 2015;83:2319-2325. PMID:26426142