Publication no. C-2004-0203-03R |  VIEW ARTICLE

Biochemical Characterization of gamma-75k Secalins of Rye II. Disulfide Bonds.

Claudia Gellrich (1), Peter Schieberle (1), and Herbert Wieser (1,2). (1) Deutsche Forschungsanstalt für Lebensmittelchemie and Kurt-Hess-Institut für Mehl- und Eiweißforschung, Lichtenbergstr. 4, D-85748 Garching. (2) Corresponding author. E-mail: <h.wieser@Lrz.tum.de> Cereal Chem. 81(2):296-299. Accepted September 1, 2003. Copyright 2004 American Association of Cereal Chemists, Inc.

Aggregated gamma-75k secalins were isolated by preparative reversed-phase (RP) HPLC of the prolamin fraction of rye flour Danko and were digested with thermolysin. The resulting peptides were preseparated by gel permeation HPLC into eight fractions (G1-G8). Peptides that were linked by disulfide bonds (cystine peptides) were identified by means of differential chromatography (RP-HPLC before and after the reduction of disulfide bonds). The cystine peptides present in fractions G3-G7 were isolated by preparative RP-HPLC and characterized by sequence analysis and, in parts, by mass spectrometry. Accordingly, the eight cysteine residues of the C-terminal domain of gamma-75k secalins were linked in the same positions as the intramolecular disulfide bonds of gamma-gliadins of wheat. The cysteine residue located at position 12 of the N-terminal domain and characteristic for gamma-75k secalins was linked by an intermolecular disulfide bond with a corresponding residue of the same protein type. This cysteine residue is likely to be responsible for the aggregative nature of gamma-75k secalins similar to a cysteine residue in the N-terminal domain of LMW subunits of wheat glutenin. In contrast to LMW subunits of glutenin, gamma-75k secalins do not possess an additional cysteine residue in the C-terminal domain that forms a second intermolecular disulfide bond. Therefore, the polymerization of gamma-75k secalins is limited and the formation of large gluten-like aggregates of rye storage proteins is restricted.