Three-dimensional Structure Prediction And Molecular Dynamics Simulations Of The N-terminal Domain Of Wheat High Molecular Weight Glutenin Subunit 1By15

Gluten proteins consist of monomeric gliadins and polymeric glutenins. Their attributes and proportion confer the dough unique rheological property. Glutenin is the main source of elastic and baking properties in the dough and its molecular structure determines the interactions between gluten proteins during flour processing. Glutenins exist as nonhomogeneous macropolymers formed by intra- or inter- disulfide-bonded linkage and aggregate to form the gluten network. Disulfide bonds and hydrogen bonds between polypeptide chains play a key role in determining the intensity property of dough. In the reductive condition, glutenin can be divided into high molecular weight glutenin (HMW-GS) and low molecular weight glutenin (LMW-GS). There are two approaches in researching molecular structure of gluenin: 1.utilizing x-ray crystal diffraction, NMR or spectrum techniques; 2.a bioinformatics strategy, three-dimensional structure prediction is applied in protein structure modeling studies.Using secondary structure prediction, fold-recognition, 3D structure modeling and molecular dynamics simulation, we built three models for the N-terminal domain of HMW-GS 1By15. Analysis of these models revealed two possible ways of disulfide bridges of the five cysteine residues in N-terminal domain of y-type HMW-GS: (1) the existence of an intrachain disulfide bridge between cysteines 22 and 44, leaving the three other cysteines free of engaging in intermolecular bonds; and (2) the creation of two intrachain disulfide bridges(involving cysteines 22–44 and cysteines 10–55), leaving a single cysteine(cysteine 45)for creating an intermolecular disulfide bridge. At present,there are two different views on the cysteine positions involved in disulfide linkage between y-type HMW-GS and other glutenin subunits(x-type HMW-GS and LMW-GS). Our models of the N-terminal domain of 1By15 was consistent with Kasarda's conclusion and complemented previous theories about model of gluten"backbone"formed by glutenin subunits interactions. Additionally, proteins of the cereal inhibitor family and the N-terminal domain of 1By15 are remotely homologous. This implies that the present function of the N-terminal domain of 1By15 and the function of proteins of the cereal family are more likely to have diverged over time. There still might exist a possibility for the N-terminal domain of 1By15 to have similar function. Therefore, it is necessary to test this possibility with experiment.