This domain, comprising 8 conserved cysteines, is found in the N terminus of higher multicellular animal membrane and extracellular proteins. It is postulated that this domain may play a role in the formation of protein complexes involving various protease activators and inhibitors. It is possible that some of the cysteine residues in the MANSC domain form structurally important disulfide bridges. All of the MANSC-containing proteins contain predicted transmembrane regions and signal peptides. It has been proposed that the MANSC domain in HAI-1 might function through binding with hepatocyte growth factor activator and matriptase.