Structure, assembly and targeting of wheat storage proteins

The functional properties of wheat flour in various food systems (most notably for breadmaking) are determined largely by the structures and interactions of the prolamin storage proteins, termed gliadins and glutenins. It is therefore important to understand the structures of the individual proteins, their pathways and mechanisms of synthesis and deposition, and their interactions with other flour components (for example, starch and lipids) in order to manipulate the quality of wheat for food and other uses, Me are using a range of biophysical and biochemical approaches to determine the structures of individual proteins, using fractions purified from flour or expressed in heterologous systems. We are also isolating cDNAs for proteins involved in protein folding and assembly in the endoplasmic reticulum (protein disulphide isomerase, BiP and peptidyl-proly cis-trans isomerase) and studying their interactions with gluten proteins synthesised in E. coli. This work is complemented by immunocytochemical studies of gluten protein deposition in the leaves and seeds of transgenic tobacco plants, using wild-type proteins and mutants in which specific transit-targeting sequences have been added or deleted. Taken together these results are giving a detailed picture of the structure, synthesis, assembly and deposition of wheat gluten proteins.