Interactions between Rhizobia and Lectins of Lentil, Pea, Broad Bean, and Jackbean

A quantitative method was developed to measure the binding of fluorescent-labeled lentil (Lens esculenta Moench), pea (Pisum sativum L.), broad bean (Vicia faba L.), and jackbean (Canavalia ensiformis L., DC.) lectins to various Rhizobium strains. Lentil lectin bound to three of the five Rhizobium leguminosarum strains tested. The number of lentil lectin molecules bound per R. leguminosarum 128C53 cell was 2.1 x 10(4). Lentil lectin also bound to R. japonicum 61A133. Pea and broad bean lectins bound to only two of the five strains of R. leguminosarum, whereas concanavalin A (jackbean lectin) bound to all strains of R. leguminosarum, R. phaseoli, R. japonicum, and R. sp. tested. Since these four lectins have similar sugarbinding properties but different physical properties, the variation in bindings of these lectins to various Rhizobium strains indicates that binding of lectin to Rhizobium is determined not only by the sugar specificity of the lectin but also by its physical characteristics.The binding of lentil lectin and concanavalin A to R. leguminosarum 128C53 could be inhibited by glucose, fructose, and mannose. However, even at 150 millimolar glucose, about 15% of the binding remained. The binding of lentil lectin to R. japonicum 61A133 could be inhibited by glucose but not by galactose. It is concluded that the binding site of lentil lectin to R. japonicum is different from the binding site of soybean lectin to R. japonicum.