This domain has a four-helix bundle structure. It contains four disulfide bonds, of which three function to keep the C- and N-terminal parts of the molecule in place [1].

1: Crystal structure of hydrophobic protein from soybean; a member of a new cysteine-rich family. Baud F, Pebay-Peyroula E, Cohen-Addad C, Odani S, Lehmann MS; J Mol Biol. 1993;231:877-887. PMID:8515457