Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 15, 2013
Publication Date: February 15, 2013
Citation: Kasarda, D.D., Adelsteins, E., Lew, E., Lazo, G.R., Altenbach, S.B. 2013. Characterization of a novel wheat endosperm protein belonging to the prolamin superfamily. Journal of Agricultural and Food Chemistry. 61:2407-2417. Interpretive Summary: The many different proteins found in wheat flour (endosperm) are of interest for several reasons, including their role in bread-making quality, their activity in celiac disease, and activity in producing the symptoms of allergy in susceptible individuals. Although many components have been characterized, there remain a considerable number that have not. Here we describe the purification and characterization of a new component, which we call “farinin.” This protein shows evidence of modification by an asparagine endoproteinase indicating that such enzymes, usually associated with protein processing of globulins in other species, are active in wheat. The likelihood that this new protein is an important allergen is discussed and computer modeling of the protein suggests that it might be crystallized for complete 3-D structure determination, which would enable analysis of the basis for its allergenicity and a possible role in determining wheat quality differences.
Technical Abstract: Starch granule surface-associated proteins were separated by HPLC and identified by direct protein sequencing. Among the proteins identified was one that consisted of two polypeptide chains of 11 kDa and 19 kDa linked by disulfide bonds. Sequencing of tryptic peptides from each of the polypeptide chains revealed similarities between some of the peptides and avenin-like b proteins encoded by partial cDNAs in NCBI. To identify a contiguous sequence that matched all of the peptides, contigs encoding three avenin-like b proteins were constructed from ESTs of the cultivar Butte 86. All peptide sequences were found in a protein encoded by one of these contigs that had not been identified previously. Comparison of protein and DNA sequences indicated that the two polypeptide chains were derived from a parent protein that had been cleaved at the C-terminal position of an asparagine residue. This type of cleavage suggested a relationship to the processing of storage proteins in dicots. Interestingly, only one of the three contigs encoded a protein containing this asparagine residue. Evolutionary relationships of the protein are discussed and a simple computer molecular model was constructed based on the sequence and hypothetical disulfide bond arrangements. The name farinins is suggested for the avenin-like proteins of wheat. On the basis of its sequence, the new protein was likely to be allergenic but unlikely to be active in celiac disease.