Acid-adaptive protein possibly of physiological significance when H.pylori colonises the human stomach, which adopts a unique four alpha-helical triangular conformations. The biologically active form is thought to be a tetramer. The protein is expressed along with six other proteins, some of which are related to iron storage and haem biosynthesis [1].

1: Crystal structure of HP0242, a hypothetical protein from Helicobacter pylori with a novel fold. Tsai JY, Chen BT, Cheng HC, Chen HY, Hsaio NW, Lyu PC, Sun YJ; Proteins. 2006;62:1138-1143. PMID:16395670