Serpins from wheat grain

Abstract

Wheat serpin genes have been identified by Southern blot hybridization with three distinct barley protein Z probes. Immunoblot analysis with a monoclonal antibody towards barley protein Z confirmed expression of related M r ~ 40 kDa proteins in wheat grain. The wheat serpins were extracted under reducing conditions and separated from β-amylase and other seed proteins by thiophilic adsorption and anion-exchange chromatography. One molecular form possessing chymotrypsin inhibitory activity was isolated in a reactive site cleaved form on a chymotrypsin affinity column. N-terminal amino acid sequences of a CNBr fragment and of the C-terminal peptide from the cleaved inhibitor (M r 4574 ± 4 Da) verified homology with barley protein Z and mammalian serpins. The native inhibitory serpin was demonstrated to form an SDS-stable complex with α-chymotrypsin.