Hemerythrin from Lingula unguis consists of two different subunits, alpha and beta.

Hemerythrin, a non-heme Fe-protein, of Lingula unguis has an octamer structure. We demonstrated that the protein is composed of two distinct subunits (alpha and beta), in equal amounts by investigation of their composition and partial terminal sequence. The cross-linking reaction of the native protein with dithiobis-(succinimidyl propionate) provided evidence for the presence of a dimer composed of alpha and beta subunits.