Cereal Chem 60:1. | VIEW
Extraction, Separation, and Polymorphism of the Prolamin Storage Proteins (Secalins) of Rye.
P. R. Shewry, S. Parmar, and B. J. Miflin. Copyright 1983 by the American Association of Cereal Chemists, Inc.
The amounts of secalin extracted from milled grain of rye with three alcohol/water mixtures were compared. Two sequential fractions were extracted with the solvent alone (secalin-I) and then with the solvent + 2% (v/v) 2-mercaptoethanol (secalin-II). The relative amounts of nitrogen recovered in the two fractions extracted at 20 C were greatest with 50% propan-1-ol (32.5%) and least with 60% ethanol (24%). The two fractions extracted with 50% propan-1-ol at 60 C contained more than 40% of the nitrogen, although electrophoresis showed some nonsecalin components in the secalin-II. Sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE) of the fractions showed four groups of polypeptides called high molecular weight (HMW) secalins, 75,000-dalton gamma-secalins, omega-secalins, and 40,000-dalton gamma-secalins. Secalin-II contained mainly HMW secalins and 75,000-dalton gamma-secalins. SDS- PAGE of unreduced and reduced secalin-I indicated that the HMW and 75,000-dalton gamma-secalins were extracted as disulfide-linked aggregates. Fractions were also separated by electrophoresis at pH 3.2 and by three two-dimensional procedures. These showed that the 40,000- and 75,000-dalton gamma-secalins were complex groups of polypeptides. Analysis of single seeds showed variation in secalin patterns within and between commercial varieties. This was not present in a homozygous population, and two-dimensional analysis of secalin from this line showed a smaller number of components.