Sequence homology between barley endosperm protein Z and protease inhibitors of the α₁‐antitrypsin family

Abstract

Six cDNA clones encoding parts of protein Z, a major barley endosperm albumin, have been identified. Nucleotide and amino acid sequencing have established a 180 residues long C‐terminal amino acid sequence of protein Z as well as two minor amino acid sequences (14 and 7 residues). These sequences show that barley protein Z is homologous with human α 1 ‐antitrypsin, human otj‐antichymotrypsin, human antithrombin III, mouse contrapsin and chicken ovalbumin (26–32% of the 180 residues in the C‐terminal sequence in identical positions). The sequence homology and specific cleavage of protein Z at a bond corresponding to the reactive site of the inhibitors indicate a possible inhibitory function. Inhibition of microbial or pancreatic serine proteases could, however, not be associated with protein Z.