Navy (haricot)-bean (Phaseolus vulgaris) lectin. Isolation and characterization of two components from a toxic agglutinating extract

Abstract

Two protein components were isolated in a highly purified state from a toxic fraction from the navy (haricot) bean (Phaseolus vulgaris). One, a lectin, strongly agglutinated horse erythrocytes and leucocytes, agglutination being readily observable with both types of cell at a lectin concentration of 4mug/ml. The other component (component 1), although possessing some similarity in composition, was thought to be non-agglutinating or, at most, only very weakly so. Component 1 had a mol.wt. of about 143000 and a subunit mol.wt. of about 37000, suggesting a tetrameric structure probably with identical subunits. Alanine was the only N-terminal amino acid identified and the molecule was notable in being devoid of tryptophan and cysteine, low in methionine and high in leucine, glutamic acid and aspartic acid. The lectin was somewhat smaller (mol.wt. about 114000) and apparently also composed of four identical subunits of mol.wt. about 30000. Dansylation showed that arginine occupied the N-terminus of the polypeptide chain. Aspartic acid, serine, threonine and leucine were the predominant amino acids of the lectin, and the sulphur-containing amino acids were entirely absent. Both constituents were glycoproteins and the compositions of the carbohydrate portions (4.9% for component 1 and 8.1% for the lectin) were generally similar, consisting of mannose and glucosamine with smaller amounts of glucose and traces of xylose and arabinose.

A homotetrameric agglutinin with antiproliferative and mitogenic activities from haricot beans

“…An eight-fold increase in specific activity of the agglutinin [ Table 1] was obtained. This compares favorably with the 5.7-fold increase in specific activity obtained by Andrews [19]. In the investigation of Andrews [19], DEAE-cellulose and Sephadex G200 are effective in removing inactive materials.…”

“…This compares favorably with the 5.7-fold increase in specific activity obtained by Andrews [19]. In the investigation of Andrews [19], DEAE-cellulose and Sephadex G200 are effective in removing inactive materials. The homotetrameric nature of haricot bean agglutinin is disclosed by the presence of a single 33 kDa band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, a single 130 kDa peak in gel filtration, and a single N-terminal sequence.…”

“…However, no sequence information is available. The isolated agglutinin has not been examined with regard to biological activities such as mitogenic, antiproliferative and HIV-1 reverse transcriptase inhibitory activities which are characteristic of some lectins [19]. The objective of the present study was to purify and partially characterize haricot bean agglutinin.…”

“…Research on haricot beans is restricted to only an early report on isolation of haricot bean agglutinin [19]. Haricot bean/agglutinin is a glycoprotein composed of four subunits each with a molecular mass of 30 kDa.…”

Natural toxicants in selected leguminous seeds with special reference to their metabolism and behaviour on cooking and processing

“…Andrews (1974) isolated and purified two glycoproteins from simple saline extracts of navy beans; one of these very pure glycoproteins (called lectin) strongly agglutinated horse erythrocytes and leucocytes. Each of the fractions obtained during the purification steps were incorporated by Andrews & Jayne-Williams (1974) into an experimental diet fed to conventional Japanese quail and it was found that most of the growth depression and lethality observed was associated with the fraction containing the phytohaemaggtutinins.…”