Communicated by B. S. Gill Y.-K. Lee · F. Bekes · P. Gras · M. Ciaffi M. K. Morell · R. Appels ( ) CSIRO-Plant Industry, PO Box 1600, Canberra, ACT 2601, Australia Theor Appl Genet (1999) 98 : 149 —155  Springer-Verlag 1999 Y.-K. Lee · F. Bekes · P. Gras · M. Ciaffi M. K. Morell · R. Appels The low-molecular-weight glutenin subunit proteins of primitive wheats. IV. Functional properties of products from individual genes Received: 24 November 1997 / Accepted: 18 August 1998 Abstract Three genes encoding the low-molecular- weight glutenin subunits (LMW-GSs), LMWG-E2 and LMWG-E4, from A-genome diploid wheat species, and LMW-16/10 from a D-genome diploid wheat, were expressed in bacteria. The respective proteins were pro- duced on a relatively large scale and compared with respect to their effects on flour-processing properties such as dough mixing, extensibility and maximum res- istance; these are important features in the end-use of wheat for producing food products. The LMWG-E2 and LMWG-E4 proteins caused significant increases in peak resistance and mixing time, compared to the con- trol, when incorporated into dough preparations. The LMWG-16/10 protein was qualitatively less effective in producing these changes. All three proteins also confer- red varying degrees of decrease in dough breakdown. LMWG-E2 and LMWG-E4 caused significant in- creases in dough extensibility, and decreases in max- imum resistance, relative to the control. LMW-16/10 did not show a significant effect on extensibility but showed a significant decrease in maximum resistance. The refinement of relating specific features of the struc- ture of the LMW-GS genes to the functional properties of their respective proteins is discussed. Key words Low-weight glutenin subunits · Single proteins · extensibility · Dough properties Introduction The low-molecular-weight glutenin subunits (LMW- GSs) account for 40% of wheat gluten protein content by mass, and these proteins are considered to signifi- cantly affect dough-quality characteristics (Gupta and Shepherd 1988; Gupta et al. 1989; Pogna et al. 1990; Gupta et al. 1991; Nieto-Taladriz et al. 1994; Sissons et al. 1997). In particular, LMW-GS fractions have been found to be significantly correlated with dough extensibility (Gupta and Shepherd 1988; Gupta et al. 1989; Metakovsky et al. 1990; Gupta et al. 1991); it has also been shown that these proteins cause increased dough-mixing time (Sissons et al. 1997). Features of these proteins, such as the distribution of the cysteine residues available for intermolecular disulphide bonds (reviewed by Shewry and Tatham 1997), as well as their overall amino-acid compositions involved in non- covalent bonds (Bloksma and Bushuk 1988; Pomeranz 1988), are important in determining the rheological properties of dough. These properties are critical in the food uses of wheat flour. Using the LMW-GSs produced from a bacterial ex- pression system, 2-g Mixograph and small-scale exten- sibility tests can be conducted to study the functional behaviour of the LMW-GSs in dough. There have been several studies on the expression of individual wheat storage proteins using various systems; HMW-GSs in Escherichia coli (Bartels et al. 1985; Galili 1989), gliadins in the yeast Saccharomyces cerevisiae (Neill et al. 1987; Scheets and Hedgcoth 1989; Blechl et al. 1992), LMW-GSs in insect cells using a baculovirus vector (Thompson et al. 1994), and LMW-GSs in E. coli (Ciaffi et al. 1998). However, expression of a LMW-GS derived from A- and D-genome diploid wheats has not yet been reported. In the present study three bacterially synthesised LMW-GSs, LMWG-E2, LMWG-E4 (Lee et al. 1998) and LMW-16/10 (Ciaffi et al. 1998), were compared with respect to their effects on flour process- ing properties such as dough mixing, extensibility and maximum resistance. Reconstitution studies that combine isolated wheat flour components to form a mixture that behaves as normal flour are a powerful means for determining the