The subcellular localizations of the Dolichos biflorus seed lectin and the structurally related lectin (cross-reactive material [CRMI) from the stems and leaves of this plant were determined by immunofluorescence, immunocytochemistry, and cell fractionation procedures. Subcellular fractionation of the cotyledons using a nonaqueous procedure to minimize disruption of the protein bodies showed that the majority of the seed lectin was associated with the protein body fraction and some lectin was also present in the starch granules. Immunofluorescence and immunocytochemistry at the light microscopic level showed that the seed lectin was mainly localized at the peripheries of these organelles. Lectin was also found in the cytoplasm of the cells, although the amount appeared to be dependent upon the degree of protein body disruption.Immunofluorescence and immunocytochemistry studies of the stem and leaf lectin (CRM) indicated that a significant portion of this lectin may be associated with the cell walls, although lectin was also seen in the cytoplasm of plasmolyzed cells. Extraction and cell fractionation studies showed that a large portion of the CRM is readily solubilized and most of the remainder is pelleted at 1000g. The CRM can be extracted from these pellets by treatment with cellulase and pectinase; other reagents such as NaCI, detergents, and EDTA could also release significant amounts of CRM. These studies suggest that the CRM is noncovalently bound to the cell walls. A comparison of the distribution of exogenously supplied IlIIICRM with the endogenous CRM during extraction and cell fractionation indicates that soluble CRM is not adsorbed to the 1000g pellet during fractionation.The different subcellular distributions of these two structurally related lectins suggest that different tissues of the same plant may utilize lectins for different functions.The seeds of the Dolichos biflorus plant contain a lectin that is specific for terminal nonreducing a-N-acetylgalactosamine residues (13). This lectin is localized in the cotyledons where it accounts for about 10% of the nitrogen in the soluble mature seed extract. Upon germination of the seeds, the seed lectin disappears at about the same rate as the other cotyledon proteins (31). Peptide mapping studies and COOH-terminal amino acid analyses indicate that these subunits are identical to one another, except at their COOH-terminal ends where subunit I appears to be slightly longer than subunit 11 (6,7,29). Despite these similarities, the carbohydrate-binding activity of the lectin appears to reside in subunit 1 (12).Although the seed lectin has not been detected in other parts of the plant at any stage of its life cycle, the stems and leaves of the plant contain a glycoprotein that cross-reacts with antibodies to the seed lectin (31). This CRM' resembles the seed lectin in its amino acid and carbohydrate composition and is a 70,000 mol wt dimer consisting of one subunit with an electrophoretic mobility identical to subunit I of the seed lectin and anot...

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Further studies, using gel filtration on Sephadex G-200 columns, have confirmed and extended the similarities between the major proteins of boar seminal plasma and the vesicular secretion. The haemagglutinin in the vesicular secretion has been shown, by red cell agglutination, to occur as a distinct peak masked by the greater protein content of Fraction A. Completely fresh vesicular secretion kept at 37\s=deg\C and studied at this temperature within 30 min of slaughter, presents an identical gel filtration pattern.