Heritable Variation in a Polypeptide Subunit of the Major Storage Protein of the Bean, Phaseolus vulgaris L.

Abstract

Electrophoretic analysis of the major seed protein, GI globulin, from four strains of Phaseolus vulgaris L. revealed a three-banded pattern for two strains having a high methionine content (BBL 240 and PI 302,542). The other two strains (PI 207,227 and P1 229,815) known to have a lower seed methionine content, had a two-banded subunit pattern for the GI globulin. Analytical ultracentrifugation confirmed that globulin from the two-banded strains underwent pHdependent reversible dissociation similar to that previously found for a three-banded cultivar; additionally, the protomer molecular weight showed that three subunits of about 50,000 molecular weight each were present in the GI globulin of the two-banded strain. Gel patterns of Gl globulin from the two strains used as parents, BBL 240 and PI 229,815, showed differences in the largest subunit, which appeared as either a 53,000 molecular weight polypeptide known to be present in the three-banded strain, or While soybeans have the highest protein content and economic value, the oil present in these seeds is a hindrance to protein studies, and seeds of Phaseolus vulgaris L. were selected as the preferred material. Dry seeds of P. vulgaris contain 20 to 30% protein by weight, depending on the cultivar (5). Of this protein, 50 to 75 % is globulin (requiring appreciable salt for solubility) which can be separated into two fractions. In Osborne's studies on legumes he adopted the term legumin (first used by Braconnot in 1827) for the fraction requiring the highest level of salt for solubility, and coined the term vicilin for the fraction soluble in lower salt concentrations (9). Through the years, misuse of these terms has occurred; they have been applied to proteins from many genera despite the differing properties of protein in a given fraction from species to species. To avoid the resulting confusion, we designated the globulin fraction which first precipitates on addition of water to a saline solution of P. vulgaris protein as the Gl fraction, and the second fraction (obtained by extensive dialysis) as the G2 fraction (7).Despite the apparently simple separation of the two globulin fractions on the basis of solubility, great difficulty has been experienced in obtaining them free from traces of cross-contamination. We developed an acidic extraction procedure (7) which achieves this goal, permitting characterization of the Gl and G2 globulin fractions (15). Recent articles (12, 18) have described separation of globulins using zone precipitation, which performs the same function as our isoelectric separation, but is lengthier and limits the amount of material that can be handled.Although the G2 fraction gives a single boundary sedimenting at 6.6S in the analytical ultracentrifuge (16), it is not homogeneous, and contains several growth-inhibiting substances. This fraction has a high content of sugar-containing proteins, and a major component, glycoprotein I (10), possesses hemagglutinating properties, i.e., it is a lectin. Purification of lectin from Phas...

Genetic variability in the structure of the α-subunits of legumin from Pisum—a two-dimensional gel electrophoresis study

“…There is some evidence, discussed below, which indicates gene duplication of ccM loci and suggests that ccM..subunit genes may be closely linked. Little information exists on the genetics of the seed storage protein subunits from any legume, other than the work of Romero et al (1975) and Hall et al (1977) on heritable variation in a subunit of a major storage protein of Phaseolus vulgaris and the study of Pisum sativum by Thomson and Schroeder (1978). These latter authors have described five genetic systems (LA-LE) determining the structure of Pisum legumin.…”

Determination of Phaseolin Types in Common Bean (Phaseolus vulgaris) Varieties from Turkey

“…The molecular weights of the bands obtained in this study correlates with those reported by other researchers. However the method of extraction and characterization of phaseolin can lead to different results obtained by different laboratories (Derbyshire et al,1976).SDS-PAGE analysis of phaseolin has been utilized worldwide as an effective tool in analyzing genetic variability, evolutionary relationships and correlation between molecular weight of the band and genotype among bean populations (Brown et al, 1981b;Mcleester et al, 1973;Romero et al, 1975;Gepts, 1998;Singh, 2001;Rodiňo et al, 2001b).We have also observed that SDS-PAGE analysis was useful in tracking the origins of bean genotypes that have been dispersed into various regions because PAGE analyses revealed any changes in genetic variability during the cultivation process. These changes in the Phaseolin locus (Phs) have been shown in Mesoamerican genotypes rather than Andean genotypes (Gepts, 1993;Kami et al, 1995;Chacon et al, 2005).…”

Cell-free Synthesis of the Major Storage Protein of the Bean, Phaseolus vulgaris L.

“…4) show that the subunits are translated individually, as the SDS treatment used will not break covalent bonds. Genetic analysis of subunit patterns from different strains of Phaseolus vulgaris has shown heritable variation of the large subunit of GI independent of the other subunits (17). Taken together, the evidence from the in vitro studies and from genetic analysis makes it almost certain that the GI subunits are under control of separate genes.…”

“…In previous papers we have described the isolation (15) and characterization (22,23) of Gl globulin. In an accompanying article (17) we describe the inheritance of the largest of the three component polypeptide subunits of GI (15). Developing seeds (12-18 mm long) were used.…”