The complete primary structure of a unique mannose/glucose-specific lectin from field bean (Dolichos lab lab)

Abstract

The complete amino acid sequence of two non-identical subunits of the glucose/mannose-specific lectin from Dolichos lab lab (field bean) has been determined by sequential Edman analyses of the intact subunits and peptides derived by enzymatic and chemical cleavage. Peptides were purified by reverse phase high performance liquid chromatography and ion pair chromatography. The D. lab lab lectin is a glycoprotein having two polypeptide chains of 132 and 105 amino acid residues. The amino acid sequence of the D. lab lab lectin is compared with the various lectins of the family Leguminosae. The D. lab lab lectin is the only species of the tribe Phaseoleae that contains two nonidentical subunits of almost equal size and that shows a specificity to glucose/mannose. The lectin shows a greater homology to the glucose/mannose-specific lectins, especially concanavalin A. The unique subunit architecture of the D. lab lab lectin indicates the presence of new post-translational cleavage sites.