PURIFICATION OF A NOVEL SERPIN-LIKE PROTEIN FROM BOVINE BRAIN

We purified a novel serine proteinase inhibitor (serpin)-like protein from the bovine brain and named it B-43 from its molecular mass, 43 kD a. A cleaved peptide from B-43 was copurified with the native B-43. Pa rtial amino acid sequencing of the purified B-43 showed that this prot ein was homologous to glia-derived nexin/protease nexin-1 (GDN/PN-1), plasminogen activator inhibitor 2, leukocyte elastase inhibitor (LEI) and placental thrombin inhibitor (PTI) among the serpins. Although B-4 3 had a similar amino acid composition to these serpins, the biochemic al features of B-43 were different from them. B-43 did not form sodium dodecyl sulfate (SDS)-resistant serpin-proteinase complexes with thro mbin, urokinase, pancreatic elastase and plasmin, suggesting that thes e proteinases were not the targets of B-43. In contrast to GDN/PN-1, B -43 did not have an affinity for heparin. B-43, having different bioch emical properties from GDN/PN-1, appears to be an additional serpin ex pressed in the brain.