A MUTATION UNIQUE IN SERINE-PROTEASE INHIBITORS (SERPINS) IDENTIFIED IN A FAMILY WITH TYPE-II HEREDITARY ANGIONEUROTIC-EDEMA

Background: Hereditary angioneurotic edema (HANE) is an autosomal domi nant disease due to genetic alterations at the Cl inhibitor gene. Muta tions within the Cl inhibitor gene are responsible for the molecular d efect in type II HANE. Most of the dysfunctional proteins result from mutations involving the Arg-444 (the P-1 site of the reactive center) or amino acids NH2-terminal to the reactive center. Materials and Meth ods: We have studied a Spanish family with type II HANE by using polym erase chain reaction (PCR) to amplify the exon eight of the Cl inhibit or gene. The purified 338-bp PCR product was subcloned and transformed into competent cells. After overnight cultures, we extracted the clon ing vector from the positive colonies and sequenced both strands of th e PCR product from each patient and healthy members of the family. Res ults: We show that affected individuals in this family have a missense mutation, changing an adenine to cytosine in the codon 445. This subs titution changes threonine al the P-1' site of the reactive center to a proline. This mutation generates a new restriction site, recognized by Bsi YI. Conclusions: To our knowledge, this is the first molecular defect characterized in a Spanish family with type II HANE, and to dat e, this is the first reported mutation at the P-1' site of the reactiv e center in individuals with type II HANE. This new mutation located a t the reactive center emphasizes once more time the enormous heterogen eity of this gene.