Inter Alpha-Globulin Inhibitor H3 (ITIH3)

Enghild et al. (1989) found that one ITI member, the pre-alpha-trypsin inhibitor (P-alpha-I), is an approximately 130-kD protein that contains the mature ITIH3 heavy chain (HC3) and a 30-kD subunit. Bourguignon et al. (1993) stated that P-alpha-I is composed of HC3 covalently linked to bikunin, a Kunitz-type protease inhibitor. They reported that the 885-amino acid H3 precursor protein contains a 10-amino acid propeptide and a 19-amino acid signal peptide. Before or during linkage to bikunin, the C-terminal 238 amino acids are cleaved to produce mature HC3. H3 shares 54% and 41% identity with the H1 and H2 precursor proteins, respectively. Diarra-Mehrpour et al. (1998) corrected the cDNA sequence reported by Bourguignon et al. (1993).