Heterologous expression and dough mixing studies of wild-type and mutant C hordeins

Wild type and mutant (cysteine-containing) forms of C hordein were expressed in Escherichia coli. Incorporation of a mutant form with N-and C-terminal cysteine residues into dough using a 2g Mixograph showed similar positive effects on dough strength to the incorporation of HMW subunit 1Bx7. Go-incorporation showed that the effects of the two proteins were additive. In contrast, the incorporation of wild type C hordein or mutants with single cysteines at the N-or C-terminus resulted in decreased dough strength, with the two mutant forms inhibiting the positive effect of 1Bx7. Analysis of total protein extracts from the doughs indicate that the differences resulted from alterations in the proportions of gluten monomers, small gluten polymers and large gluten polymers. (C) 1998 Academic Press Limited.