EVIDENCE FOR GLYCOSYLATION OF THE HIGH-MOLECULAR-WEIGHT GLUTENIN SUBUNIT-2, SUBUNIT-7, SUBUNIT-8, AND SUBUNIT-12 FROM CHINESE SPRING AND TAM-105 WHEATS

High molecular weight glutenin subunits (HMW-GS) of wheat, obtained by a modification of the method of Burnouf and Bietz (1989), were charac terized by isoelectric focusing, lectin binding, and gas chromatograph y-mass spectroscopy. The purification method involved a dimethyl sulfo xide extraction of flour, followed by reduction and alkylation of the proteins. The extracted subunits were separated on, and excised from, sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels. These subunits, when analyzed by reversed phase high-performance liquid chro matography, eluted at approximately 45% acetonitrile, indicating that, under these conditions, they were more hydrophobic (approximately 30% ) than previously reported (Burnouf and Bietz 1989, Wieser and Belitz 1990). The purified HMW-GS were reelectrophoresed on sodium dodecyl su lfate polyacrylamide gel electrophoresis minigels and silver-stained. A single band for each subunit provided an indication of the purity of the subunit. Further characterization of the purified HMW-GS revealed that the proteins were glycosylated. Lectin-binding analyses showed t hat the terminal carbohydrate moiety of these glycoproteins was mannos e. Gas chromatography-mass spectroscopy analyses confirmed the presenc e of mannose in the total glutenin preparations as well as in each of the individual purified HMW-GS. Gas chromatography-mass spectroscopy a nalyses also detected glucose and N-acetyl glucosamine in the individu al purified HMW-GS.