Characterization of a monoclonal antibody specific for HMW subunits of glutenin and its use to investigate glutenin polymers

A monoclonal antibody, IFRN 1602, has been developed to a synthetic peptide based on the sequence (94)GSVTCPQQV(101) of HMW subunit 1Dx5. The antibody bound strongly to the synthetic peptide based on the cognate sequence of H MW subunit 1Dx2 which contains a serine instead of a cysteine residue. Howe ver, it recognized the immunizing peptide by enzyme-linked immunosorbent as say (ELISA) only poorly, probably because the peptide exists as a disulfide -bonded dimer under the assay conditions. From immunoblotting studies again st a wide range of wheat varieties, IFRN 1602 was shown to primarily recogn ize x-type HMW subunits of glutenin encoded on chromosomes 1A and 1D, cross -reacting weakly with the 1A and 1D y-type subunits. It did not bind to any of the 1B-encoded subunits. The Mab also recognized a small number of poly peptides of greater mobility than HMW subunits which were not visible on th e stained gels and occurred only in the presence of specific IA and ID x-ty pe HMW subunits. Such polypeptides were not present in a preparation of rec ombinant subunit 2, suggesting that they are modified forms of the subunits which arise in the seed perhaps by processing of the associated subunits. When used to probe partially reduced glutenin; IFRN 1602 bound to 1Dx5-1Dy1 0 dimers. As the Mab reacted primarily with Cys(97) of 1Dx5 in a reduced fo rm, these data suggest that this residue is not involved in either intra- o r intermolecular disulfide bond in the HMW subunit dimers. Thus, Cys(97) of 1Dx5 may be present in gluten in a reduced form, involved in intramolecula r disulfide bonds, or linking of the HMW subunit dimers into larger polymer s.