Purification and Characterization of Arcelin Seed Protein from Common Bean

Abstract

Arcelin, a seed protein originally discovered in wild bean accessions, was purified, characterized, and compared to phaseolin, the major seed protein of common bean, and to phytohemagglutinin (PHA), the major bean seed lectin. Arcelin and PHA has several characteristics in common.Both were glycoproteins having similar subunit M, deglycosylated Mn and amino acid compositions. The two proteins were related antigenically and they had the same developmental timing of accumulation. Arcelin also had some hemagglutinating activity, a characteristic associated with lectins. However, several features distinguished arcelin from PHA. Arcelin had a more basic isoelectric point than PHA, greater numbers of basic amino acid residues, additional cysteine residues, and one methionine residue, which PHA lacks. Native PHA protein is a tetramer of subunits, and although a small component of native arcelin protein was also tetrameric, most of the arcelin preparation was dimeric. The hemagglutinating activity ofarcelin was specific only for some pronase-treated erythrocytes. It did not agglutinate native erythrocytes, nor did it bind to thyroglobulin or fetuin aff'mity resins as did PHA. Although arcelin has lectin-like properties, we believe the distinctions between arcelin and PHA warrant the designation of arcelin as a unique bean seed protein.was co-dominant with respect to each other and dominant with respect to alleles for the absence of arcelin. Genes controlling arcelin expression were tightly linked (<0.3% recombination) to those controlling PHA expression. The presence of arcelin in wild bean accessions was correlated with high levels of resistance to two bruchid beetle species (19,24).Although arcelin protein has a different electrophoretic mobility than other major seed proteins, it is not known whether arcelins represent a truly distinct class of seed proteins. The relationship of arcelin to other seed proteins is particularly interesting in light of the tight linkage between arcelin and PHA genes. In this study, we report on the purification and characteriz,tion of the arcelin-1 variant and compare its properties to those of PHA and phaseolin seed proteins. The major seed storage proteins of cultivated common bean (Phaseolus vulgaris) are phaseolin and PHA,2 also referred to as bean lectin. In several wild bean accessions, a third important protein fraction has been observed which had not been described previously in bean cultivars (19,23). This fraction was discovered as a major seed protein having a different electrophoretic mobility than either phaseolin or PHA with which it occurred in seeds of some wild beans. Four electrophoretic variants of this protein were observed which consisted of distinct groups of polypeptides having similar mobilities on two-dimensional gels. This protein was named arcelin and the variants were designated arcelin-1, 2, 3, and 4.There has been only limited characterization of arcelin, but the protein and its genetic control have several interesting features. Arcelin was shown to o...

Isolation and Partial Characterization of a Seed Lectin from Tepary Bean that Delays Bruchid Beetle Development

“…That protein was later described and named arcelin ( 14). The bioactivity of arcelin against an economically important seed predator has been confirmed (15).…”

Characterization and Comparison of Arcelin Seed Protein Variants from Common Bean

“…Using artificial seeds reconstituted from bean flour with the addition of purified arcelin protein, arcelin-1 was shown to be the component of the wild lines that confers resistance to Z. subfasciatus (18). Arcelin and PHA isolated from an arcelin-1-containing line had similar solubility properties, subunit Mrs, deglycosylated Mrs, and amino acid compositions; however, they had very different isoelectric points, and PHA agglutinated native erythrocytes but arcelin agglutinated only Pronase-treated cells (20). These similarities and differences might be explained by the observation that the cDNA nucleotide-derived amino acid sequence of arcelin-1 is approximately 60% identical to PHA-E and PHA-L (18).…”

“…These similarities and differences might be explained by the observation that the cDNA nucleotide-derived amino acid sequence of arcelin-1 is approximately 60% identical to PHA-E and PHA-L (18). Arcelin has one methionine (PHA-E and PHA-L have no methionine) and additional attached oligosaccharide residues (18,20) that may affect the chemistry and conformation of the mature protein.…”

Synthesis of Lectin-Like Protein in Developing Cotyledons of Normal and Phytohemagglutinin-Deficient Phaseolus vulgaris

“…Cotyledons were homogenized and an ER-enriched organelle fraction isolated as described (26). To inhibit N-glycosylation, cotyledons were preincubated for 3 h with 20 ,uL of tunicamycin (500 gg/mL in 1 mM NaOH, Sigma), before labeling with…”

“…The P. vulgaris genome contains a number of sequences that hybridize at low stringency with PHA clones (4,23), indicating that there may be a number of PHA-like genes. Recent work by Osborn et al (18,20) shows that some wild accessions of bean contain a PHA-like gene that encodes the seed protein arcelin; this protein is toxic to an important bean bruchid pest, Zabrotes subfasciatus, which is not affected by PHA. Another gene, which is expressed in developing seeds and exhibits sequence homology with respect to PHA and arcelin genes, has been characterized by Hoffman et al (1 1, 13).…”