An Electrophoretic Investigation of Groundnut Proteins: The Structure of Arachins a and B

Abstract

1. The proteins of the groundnut cotyledon have been fractionated and analysed by DEAE-Sephadex chromatography and acrylamide-gel electrophoresis. Seventeen components were detected. 2. A new method is described for the preparation of arachin, using calcium precipitation. The product contains at least 99% of arachin. 3. The theory of acrylamide-gel electrophoresis is developed and applied to the arachin system to predict the molecular weight of one sub-unit of arachin. 4. A variant form of arachin, arachin B, has been discovered. Of 81 nuts, 27 contained only arachin B, 53 contained both arachin A and B, and one contained arachin A only. This is almost certainly a polymorphism of arachin; this is the first example of polymorphism to be reported in plant proteins. 5. A combination of controlled denaturation, electrophoretic analysis, ultracentrifuge and Sephadex filtration data has shown that arachin A contains four different kinds of peptide chains (alpha, beta, gamma and delta). Arachin B contains only beta, gamma and delta chains. 6. The most probable structure for arachin B, mol.wt. 330000 form, is 8 beta, 2 gamma and 2 delta chains, and for arachin A, 4 alpha, 4 beta, 2 gamma and 2 delta chains. Arachin without beta chains was not found. 7. The alpha and beta chains have mol.wts. of about 35000 and the gamma and delta chains of about 10000. 8. Three N-terminal groups were found: the alpha and beta chains both terminate in glycine; the gamma and delta chains terminate in isoleucine and glutamic acid. 9. Arachin contains no carbohydrate. 10. Disulphide bonds are not important in arachin: there are none between the alpha, beta, gamma and delta chains. 11. The amino acid compositions of arachins A and B are very similar. Glutamic acid and aspartic acid residues are exceptionally frequent.

Dissociation-Association Behavior of Arachin between Dimeric and Monomeric Forms

“…25 , 26 1 However, our results suggest that the subunit compositions of the arachin II dimer are the same as those of arachin I. So the difference between the dimers of arachins I and II in the dissociation system will not be derived from the difference in the subunit composition.…”

Comparative Studies of Subunit Compositions of Legumins from Various Cultivars ofVicia fabaL. Seeds

“…7 ) Moreover, recently, multiplicities of storage proteins have been reported for arachin of Arachis hypogaea, 25,26) legumins of Pisum sativum ll ) and Lupinus angustifolius/ 7 ) and 7S globulin of Glycine max,2S-31) Pisum sativum ll ) and Vicia jaba.…”

The Structure of Legumin, a Storage Protein of Broad Bean (Vicia faba) Seed

“…I n particular the value derived from tryptic peptides is about 20°/, high. This discrepancy could be due to limited polymorphism in the arginine and lysine sequences but the precision of the method is insufficient to justify such a conclusion although there is some evidence for polymorphism in other seed proteins [30,31]. To determine the sub-unit ratio we have used two methods neither of which gives an absolute answer and both of which require a number of assumptions.…”