Structural and Immunochemical Homologies between Foxtail Millet Glutelin 60 kDa and Starch Granule-bound Starch Synthase Proteins from Rice, Barley, Corn and Wheat Grains.

Abstract

SummaryFoxtail millet glutelin 60kDa (MG6O) was purified by preparative SDS-PAGE, and the N-terminal amino acid sequence was determined within 20 residues. The result demonstrated that the primary structure at N-terminal of MG60 was almost identical to those of the granule-bound starch synthase (GBSS) proteins from rice, barley, corn, wheat and potato. The existence of common epitopes among MG60 and GBSS proteins from these starch-storing cereals were corroborated by immunoblot analysis using antisera raised against MG60. These facts strongly suggest a close relationship between MG60-like glutelins and GBSS proteins. Key Words foxtail millet, glutelin 60kDa, N-terminal amino acid sequence, starch gran ule-bound starch synthase, antigenic homology.Our previous paper (1) indicated that the prolamins from foxtail (Italian), proso (Common) and sawa (Japanese) millet cultivars contained common epitopes among them. Since then, however, little information on the physico-or immuno-chemical properties of the mil let storage proteins has been published so far as we know. Miflin and Shewry (2) have proposed that glutelin proteins serve a metabolic and/or structural role rather than a storage function in some cereals. Recently, we purified a polypeptide a component with a molecular mass (MM) of 60 kDa (referred to as MG60) from the urea-soluble glutelin of a foxtail millet cultivar. Then, the N-terminal amino acid sequence of MG60 was determined by the method of Matsudaira (3) in order to obtain the first clue about the function of the newly obtained glutelin component.

Identification of an Abundant 56 kDa Protein Implicated in Food Allergy as Granule-Bound Starch Synthase

“…The strong reactivity of the GBSSI gene with IgE antibodies from the serum from maize-allergic patients confirms that these two proteins share a close structural relationship. This reactivity is to be expected because a previous study has shown that granule-bound starch synthase from rice, barley, corn, wheat, and foxtail millet share structural and immunological homologies . In our present study, we did not observe any IgE reactivity to proteins from soybean and peanut.…”

“…This reactivity is to be expected because a previous study has shown that granule-bound starch synthase from rice, barley, corn, wheat, and foxtail millet share structural and immunological homologies. 40 In our present study, we did not observe any IgE reactivity to proteins from soybean and peanut. Recent X-ray structure analysis of rice GBSSI has demonstrated a disulfide bond between Cys337 and Cys529.…”

Cornstarch is less allergenic than corn flour in dogs and cats previously sensitized to corn

“…Importantly, the GBSS-I was reported recently to be an allergen for both corn-sensitized humans [ 7 , 17 ] and dogs [ 9 ]. Unfortunately, because of the high homology existing between GBSSs from starch-containing plants, that the GBSS-I is an allergen leads to a high risk of IgE cross-reactivity, not only among grains [ 18 ], but also likely between grains and tubers [ 9 , 19 ]. Whether such cross-reactivity would be clinically-relevant in corn-allergic humans or dogs has not been reported yet.…”