Galactosyl-binding lectins from the tunicate Didemnum candidum. Purification and physicochemical characterization

The plasma of the ascidian Didemnum candidum possesses lectin activity directed toward galactosyl moieties. We report the purification by affinity chromatography, the physicochemical properties, amino acid composition, and partial N-terminal amino acid sequence of two galactosyl-binding lectins D. candidum lectins I and II (DCL-I and DCL-II) from the plasma of this protochordate species. Both lectins were purified by affinity chromatography (on acid-treated Sepharose 4B and asialofetuin conjugated to Sepharose 4B) to homogeneity as judged by immunoelectrophoresis, size exclusion chromatography on high performance liquid chromatography, and polyacrylamide gel electrophoresis. Isoelectric focusing in polyacrylamide gels revealed that DCL-I focuses as a family of bands at pH 3.8-5.2, while DCL-II focuses at pH 9.2-10.2. Gas chromatography analyses of alditol acetate derivatives indicated that no carbohydrate components are associated with the lectins. Approximate subunit molecular weights estimated by polyacrylamide gel electrophoresis and size exclusion chromatography on high performance liquid chromatography in 6 M guanidine HCl under reducing conditions were 13,400-14,500 for DCL-I and 14,500-15,500 for DCL-II. Native molecular weights estimated by sedimentation equilibrium were 56,600 (DCL-I) and 57,500 (DCL-II), indicating that both species are constituted by four equal-sized subunits. Frictional ratios suggested that both lectins are globular proteins. Using rabbit antisera, the two molecules appeared serologically distinct. The extinction coefficient for DCL-I was E280 mg/ml = 2.52 ml mg-1 cm-1. Circular dichroism analyses of DCL-I suggested 29% alpha-helix and 37% beta-structure in the protein. Excitation/emission fluorescence spectra for DCL-I yielded maximum excitation and emission wavelengths at 288 and 330 nm, respectively. Amino acid compositions of DCL-I and DCL-II differed mainly in the proportions of aspartic and glutamic acids, serine, alanine, cysteine, valine, phenylalanine, and histidine. Amino acid compositions of DCL-I and DCL-II were compared to each other and to immunoglobulins and putative recognition molecules by the parameter S delta Q. DCL-I exhibited similarities in amino acid composition to lectins from the tunicate Halocynthia pyriformis, the lamprey Petromyzon marinus, and the horseshoe crab Carcinoscorpius rotundicauda, rabbit C-reactive protein, and lamprey and carp immunoglobulin mu chains. DCL-II showed amino acid composition and similarities with several fish immunoglobulin light chains, immunoglobulin-related molecules isolated from mouse and marmoset T cells, and carp and goldfish immunoglobulin heavy chains.(ABSTRACT TRUNCATED AT 400 WORDS)     

Lectins from seeds of Crotalaria pallida (smooth rattlebox)

A lectin from the seeds of Crotalaria pallida (CPL), with an apparent molecular mass of 30 kDa, determined by SDS-polyacrylamide gel electrophoresis, showed human type A and B erythrocytes agglutination activity, which is inhibited by raffinose and galactose. The lectin requirement for divalent cation was demonstrated with EDTA/EGTA blocking hemagglutination activity. Although the N-terminal amino acid sequence of CPL is identical to another lectin from Crotalaria striata, which is taxonomically synonymous to Crotalaria pallida, these lectins differ in amino acid composition and hemagglutination properties.     

Anaplasma marginale, Eperythrozoon wenyoni: lectin reactions with bovine erythrocytes

Normal bovine erythrocytes were agglutinated with four of five lectins specific for different oligosaccharides. The order of reactivity was wheat germ greater than ricin greater than soybean greater than peanut. Concanavalin A did not agglutinate normal bovine erythrocytes. After neuraminidase treatment of normal bovine erythrocytes, each lectin agglutinated the cells with decreased concentrations of lectin, verifying that partial removal of sialic acid exposes more of each lectin's binding sites or alters the binding site such that fewer molecules of lectin are required to initiate agglutination. A change in agglutination of erythrocytes using soybean agglutinin and peanut agglutinin occurred when cells were obtained from cattle infected with Eperythrozoon wenyoni. The results suggested that an alteration in erythrocyte membranes occurred as a result of this infection as manifested by the increased recognition of both the soybean agglutinin and peanut agglutinin receptor carbohydrates. A similar effect was indicated with erythrocytes obtained during an acute Anaplasma marginale infection; however, an ensuing reticulocytosis masked the effect, requiring the use of fluoresceinated lectins to verify that increased binding of each lectin occurred with infected cells when compared to normal cells.     

Red cell aging results in a change of cell surface carbohydrate epitopes allowing for recognition by galactose-specific receptors of rat liver macrophages

Binding and uptake studies of in vitro aged or senescent rat erythrocytes by isolated rat liver macrophages suggest recognition by galactose-specific receptors on the cell surface of the macrophages. We analyzed carbohydrates exposed on old erythrocytes by plant lectins in an agglutination assay in comparison with freshly isolated untreated erythrocytes. Rat erythrocytes aged in vitro by storage are agglutinated by a panel of lectins that do not react with freshly isolated erythrocytes. Specificity of agglutination was shown by inhibition with monosaccharides. Antibodies eluted from senescent rat erythrocytes agglutinate in vitro aged as well as senescent rat erythrocytes, but not freshly isolated cells nor human erythrocytes. Galactose-specific lectins isolated from rat liver give similar results; they also agglutinate normal human erythrocytes. Agglutination by the liver lectin is inhibitable by galactose and N-acetylgalactosamine but not by N-acetylglucosamine or mannose. Furthermore, rat liver macrophages devoid of galactose-specific receptors show markedly reduced binding of senescent rat erythrocytes. We conclude that recognition of old rat erythrocytes is mediated by two systems: old erythrocytes expose different terminal sugar residues or a different arrangement of glycans when compared to young erythrocytes, rendering them recognizable by liver lectins and by autoantibodies.     

Plant protoplast agglutination by lectins

Concanavalin A, soybean (Glycine max L.) lectin, castor bean (Ricinus communis L.) lectin, and peanut (Arachis hypogaea L.) lectin were able to agglutinate protoplasts prepared from a variety of plant species. The seven other lectins tried were unable to agglutinate those protoplasts tested. Protoplasts prepared from 11 species were used. The lectins examined were not able to differentiate among protoplasts of different species.     

Glutaraldehyde cross-linking of lectins to marker enzymes: protection of binding site by specific sugars

The role of bound specific sugars in protecting the sugar binding activity of several galactose binding proteins during their covalent conjugation to horse radish peroxidase by glutaraldehyde-mediated cross-linking was examined by: a) affinity matrix binding of the conjugate, b) enzyme linked lectin assay and c) hemagglutination assay. During conjugation using 1% glutaraldehyde, protection of jack fruit (Artocarpus integrifolia) lectin (jacalin) activity depended on concentration of specific sugar present during conjugation; optimum protection was offered by 50 mM galactose. This indicated the presence of one or more primary groups at the binding site of jacalin, which is (are) essential for sugar binding. On the other hand, such essential amino group(s) was not indicated at the sugar binding site of the peanut lectin, bovine heart galectin or of the human serum anti alpha-galactoside antibody, since exclusion of sugar during their conjugation to HRP did not diminish sugar binding activity. The differential behavior is discussed in the light of reported differences in sugar specificities. Results indicated that sugar mediated blocking of active site may be used in characterization of the latter in lectins.     

Kluyveromyces bulgaricus yeast lectins. Isolation of N-acetylglucosamine and galactose-specific lectins: their relation with flocculation

Kluyveromyces bulgaricus is a yeast which, upon culture in a calcium-enriched glucose-peptone medium, flocculates. Its flocculation can be reversed by the addition of galactose. In this paper, it is shown that two lectins can be isolated either from the concentrated culture broth or from the supernatant of deflocculated cells suspended in galactose solution. The N-acetylglucosamine-specific lectin, at pH 7.4, agglutinates untreated sheep red blood cells, but agglutinates neither untreated rabbit red blood cells nor glutaraldehyde-fixed sheep or rabbit red blood cells. Conversely, at pH 4.5, this lectin agglutinates glutaraldehyde-fixed sheep red blood cells. The galactose-specific lectin, at pH 7.4, agglutinates both untreated and glutaraldehyde-fixed rabbit red blood cells but does not agglutinate untreated or glutaraldehyde-fixed sheep red blood cells. At pH 4.5, this lectin agglutinates both glutaraldehyde-fixed sheep and rabbit red blood cells and induces flocculation of deflocculated K. bulgaricus cells. In all cases, the agglutination and the flocculation induced by one of these two lectins were inhibited by free or conjugated N-acetyl-D-glucosamine or by free or conjugated D-galactose, respectively. No glycosylhydrolase activity could be detected in the purified lectins.     

Purification and characterization of two major lectins fromVigna mungo (blackgram)

Blackgram (Vigna mungo L. Hepper)seeds contain two galactose-specific lectins, BGL-I and BGL-II. BGL-I was partially purified into two monomeric lectins which were designated as BGL-I-1 (94 kDa) and BGL-I-2 (89 kDa). BGL-II is a monomeric lectin of 83 kDA. The purified lectins were associated with galactosidase activities. BGL-I-1 and BGL-II were copurified with α-galactosidase activity while BGL-I-2 was largely associated with β-galactosidase activity. These lectins agglutinate trypsin treated rabbit erythrocytes, but not the human erythrocytes of A, B or O groups. They were stable between pH 3·5 and 7·5 for their agglutination. The lectins did not show any metalion requirement. They were inactivated at 50°C. The lectin activity was inhibited by D-galactose (0·1 mM). The Scatchard plots of galactose binding to these lectins are nonlinear and biphasic curves indicative of multiple binding sites. The data show that the monomeric lectins have both lectin and galactosidase activities suggestive of a bifunctional protein.     

Structural and functional characterization of the GalNAc/Gal-specific lectin from the phytopathogenic ascomycete Sclerotinia sclerotiorum (Lib.) de Bary

The lectin found in mycelium and sclerotes of the phytopathogenic fungus Sclerotinia sclerotiorum is a homodimer consisting of two identical non-covalently bound subunits of 16,000 Da. CD spectra analysis revealed that the S. sclerotiorum agglutinin (SSA) contains predominantly beta-sheet structures. SSA exhibits specificity towards GalNAc whereby the hydroxyls at positions 4 and 6 of the pyranose ring play a key role in the interaction with simple sugars. The carbohydrate-binding site of SSA can also accommodate disaccharides. The N-terminal sequence of SSA shares no significant similarity with any other protein except a lectin from the Sclerotiniaceae species Ciborinia camelliae. A comparison of SSA and the lectins from C. camelliae and some previously characterized lectins indicates that the Sclerotiniaceae lectins form a homogeneous family of fungal lectins. This newly identified lectin family, which is structurally unrelated to any other family of fungal lectins, is most probably confined to the Ascomycota.     

A normal mucin-binding lectin from the sponge Craniella australiensis

A lectin, Craniella australiensis (CAL), was isolated from sponge C. australiensis by ion-exchange on DEAE-Sephacel and purified by gel filtration on Sephadex G-150 and HPLC on DEAE-5PW. The purified lectin was a trimeric protein as revealed by SDS-PAGE and MALDI-TOF analysis. SDS-PAGE showed that the CAL protein had a molecular mass of 54 kDa, and consisted of three 18 kDa subunits. Gel filtration of purified lectin on Sephadex G-200 indicates that it exists as a 54 kDa protein in its native state. The amino acid composition was rich in Thr and Glx. CAL was found to agglutinate native and trypsinized human A, B erythrocytes, and agglutinate native erythrocytes of mouse, sheep, rabbit and chicken, and trypsinized erythrocytes of sheep and rabbit. The hemagglutination activity was inhibited by glycoproteins such as PSM and asialo-PSM, but not by any of the monosaccharides tested. The activity was stable between 20 and 70 degrees C. Significant CAL activity was observed between pH 5 and 8. The lectin reaction is independent of the presence of divalent cations Ca2+ and Mg2+. The sequence of N-terminal residues of CAL was determined as TSSCQSIVVE. The lectin showed a potent mitogenic response towards BALB/c splenocytes.     

Purification and characterization of a new lectin from the hard roe of skipjack tuna,Katsuwonus pelamis

Fish eggs are known as a rich source of lectins. In this study we purified and characterized a lectin from unfertilized Katsuwonus pelamis hard roe. K. pelamis lectin (KPL) was purified by separation into two fractions above and below the molecular weight of 10kDa using ultramembrane, gel filtration on a Sephadex G-100, and affinity chromatography on an asialofetuin-Sepharose 4B. KPL is a glycoprotein of 140kDa, composed mainly of aspartic acid, glycine, phenylalanine, glutamic acid, threonine and serine residues. Analysis of the carbohydrate composition by gas-liquid chromatography indicated that carbohydrates constituted 14% of the total weight and this 14% is comprised of mannose, galactose, N-acetyl-D-glucosamine, N-acetyl-D-galactosamine, fucose, arabinose and sialic acid. The lectin is comprised of four subunits. These subunits have a molecular mass corresponding to 35kDa. KPL specifically agglutinated human blood type A erythrocytes and, in a hemagglutination inhibitory test, the potent inhibitors were D-galactose, lactose, lactosamine, asialofetuin, N-acetyl-D-galactosamine, O-serinyl-2-acetamido-2-deoxy-alpha-D-galactopyranoside and O-serinyl-2-acetamido-2-deoxy-beta-D-galactopyranoside (O-serinyl-beta-D-GalNAc). The first 10 residues of the N-terminal region were determined as PVELCDAKCT. Furthermore it was determined that the hemagglutinating activity of KPL was dependent on divalent metal cations and that the optimum activity of KPL was exhibited at 40 degrees C and pH 6.0-8.5 in the presence of Ca2+.     

紫藤凝集素的分离纯化及理化性质研究

用常规方法处理的ＤＥＡＥ离子交换纤维素柱,通过线性离子强度梯度洗脱,从紫藤种子的蛋白粗提液中得到一定纯度的紫藤凝集素。纯化的凝集素凝集兔红血球的比活提高４０倍,总活力回收率为１９．２％。紫藤凝集素的分子量经ＰＡＧＥ鉴定为２０５ｋｄ,是由两种亚基构成的四聚体,这两种亚基各有２个,分子量ＳＤＳ－ＰＡＧＥ鉴定分别为７７６００ｄ和２５１００ｄ。紫藤凝集素是一种糖蛋白,等电点约为４．６０。它可凝集人的各种血     

Vertebrate lectins, Comparison of properties of beta-galactoside- binding lectins from tissues of calf and chicken

Beta-galactoside-binding lectins were isolated from various calf tissues and from chicken hearts by affinity chromatography on asialofetuin-Sepharose, and were compared with respect to biochemical characteristics, binding properties, antigenic cross-reactivity, and cellular localization. The lectins are all thiol group-requiring, divalent cation-independent dimers, of apparent monomer mol wt 12,000 (calf lectins) or 13,000 (chicken lectin), and acidic pI. The calf lectins appear essentially identical by dodecyl sulfate-polyacrylamide gel electrophoresis, isoelectric focusing, amino acid composition, and radioimmunoassay, while the chicken lectin is distinctly different by these criteria. However, all of the lectins competed for the same binding sites on rabbit erythrocytes, and could be inhibited by the same saccharide haptens (notably lactose and thiodigalactoside). Immuno-fluorescence studies on several cultured cell lines revealed that the bovine and chicken lectins had primarily an intracellular cytoplasmic localization. The beta-galactoside-binding lectins of vertebrates appear to be species-specific rather than tissue-specific.     

Screening and preliminary characterization of hemagglutinins in Vietnamese marine algae

Extracts from 44 species of Vietnamese marine algae, including 15 Chlorophyta, 18 Rhodophyta and 11 Phaeophyta species, were examined for hemagglutination activity with a variety of different animal and human erythrocytes that were untreated or treated with enzymes. Almost all extracts showed activity toward at least one type of erythrocytes, although those from three Chlorophyta and two Rhodophyta species showed no hemagglutination with any type of erythrocytes examined. Strong activity was detected in extracts from two Chlorophyta (Anadyomene plicata and Avrainvillea erecta) and four Rhodophyta species (Gracilaria eucheumatoides, Gracilaria salicornia, Kappaphycus alvarezii, and Kappaphycus striatum) with enzyme-treated rabbit and sheep erythrocytes. The hemagglutinins of seven Chlorophyta and eight Rhodophyta species were examined for sugar-binding specificity, pH- and temperature-stability, and divalent cation-independency of hemagglutination using ammonium sulfate-precipitates prepared from their extracts. In a hemagglutination-inhibition test with various monosaccharides and glycoproteins, none of the hemagglutinins had affinity for monosaccharides, except the Codium arabicum and Gracilaria euchematoides hemagglutinins, whose activities were inhibited by both N-acetyl-d-galactosamine and N-acetyl-d-glucosamine. On the other hand, all of the hemagglutinins activities were inhibited by some glycoproteins. The inhibition profiles with glycoproteins were different depending on hemagglutinin species, and suggest the presence of lectins specific for high mannose N-glycans, complex N-glycans, or O-glycans. The activities of these algal hemagglutinins were stable over a wide range of pH and temperature, and independent of the presence of divalent cations. These results indicate that Vietnamese marine algae are a good source of novel and useful lectins.     

Some properties of the human erythrocyte receptors for Neisseria gonorrhoeae

The nature of the receptors for T1 and T4 Neisseria gonorrhoeae on erythrocytes and other cells was investigated. In general, cells of nonprimate origin contained few receptors for gonococci. Receptors for T4 gonococci were only uncovered when host cells were pretreated with trypsin. Trypsinization, while unnecessary for T1 adherence to erythrocytes, enhanced attachment in inverse proportion to original erythrocyte sensitivity. Receptors for T1 and T4 organisms on trypsinized and trypsin-neuraminidase-treated erythrocytes were blocked by concanavalin A and peanut lectins, respectively, but a distinction could be made between them with wheat germ lectin and galactose oxidase. Of a number of sugars tested as inhibitors, only D-galactose blocked adherence of T4 but was without effect on T1. While the identity of erythrocyte receptors is uncertain, likely candidates are "band 3" protein and glycophorin, by virtue of their galactose content, lectin binding capacity, and partial exposure on the outer surface of the erythrocyte.     

Evaluation of glycoconjugates on the K562 cell surface by means of lectin binding — comparison with human erythrocytes

The binding of five radiolabelled lectins (Vicia graminea, peanut,Phaseolus vulgaris isolectins E-PHA and L-PHA,Evonymus europaeus) to untreated and desialylated K562 cells and human erythrocytes was compared. The number of glycophorin A receptors recognized on the K562 cells by anti-blood group NV. graminea lectin was comparable to that found on the MN or NN erythrocyte surface. However, K562 cells had a severalfold higher number of oligosaccharide chains (presumablyO-glycosidic) which after desialylation became high-affinity receptors for peanut agglutinin, and of complex typeN-glycosidic chains available for the reaction with E-PHA and also with L-PHA (the latter lectin was not bound to erythrocytes). Moreover, K562 cells not treated with neuraminidase had a significant amount of extremely low affinity receptors for peanut agglutinin, whereas binding of this lectin to untreated erythrocytes was undetectable. On the other hand, the untreated K562 cells did not bind anti-blood group B and HE. europaeus lectin, but a small amount of binding by the desialylated cells was observed. Some other differences observed in the mode of lectin binding to K562 cells and erythrocytes are discussed.     

Isolation, molecular and biological properties of a lectin from rice embryo: relationship with wheat germ agglutinin properties

Rice lectin (Oryza sativa, var. Balilla 28) was purified from defatted embryos by aqueous acid extraction at pH 1.3 followed by ammonium sulfate precipitation between 2 and 4 M, affinity chromatography on agarose-p-aminophenyl-beta-D-N-acetylglucosamine, and gel filtration on AcA 54. The homogeneity of the lectin was checked by polyacrylamide gel electrophoresis, gel filtration, and immunodiffusion. The amino acid analysis revealed a high half-cystine content (9%) and a low aromatic and hydrophobic amino acid content. The lectin contained neither neutral carbohydrates nor amino sugars. The isoelectric point was estimated to be 8.1. The molecular weight of rice lectin was estimated to be 38,000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions showed two polypeptides with Mr 19,000 and 15,000. The circular dichroism spectrum of rice lectin in far ultraviolet was characterized by a positive maximum at 228 nm and a negative band at 203 nm suggesting the presence of a beta-pleated sheet and the absence of alpha-helix. Rice lectin had no human blood group specificity and agglutinated rabbit erythrocytes more efficiently than erythrocytes from other animal species. Furthermore, agglutination was enhanced by trypsin treatment of erythrocytes. The erythroagglutinating activity was very high since the minimal concentration needed to agglutinate erythrocytes was 0.05 micrograms/ml. Although [methyl-3H]thymidine incorporation was stimulated in human lymphocytes, rice lectin could not be considered as a mitogenic lectin since it stimulated neither blast transformation nor lymphocyte proliferation. The saccharide specificity of rice lectin was related to N-acetylglucosamine and its oligomers: N,N',N"-triacetylchitotriose was the most powerful inhibitor. Furthermore, the N-acetylneuraminic acid was not a specific rice determinant. Finally, the double immunodiffusion method revealed a cross-reactivity between rice lectin and wheat germ agglutinin, indicating that these lectins were closely antigenically related. The analogies and differences between biological and immunological properties of rice lectin and wheat germ agglutinin are discussed and the possibility of their evolution from a common ancestor is put forward.     

Purification and characterization of a lectin from wild sunflower (Helianthus tuberosus L.) tubers

A lectin (HTTL) was isolated from Helianthus tuberosus L. (wild sunflower) tubers using ion-exchange chromatography, gel filtration, and affinity chromatography. The lectin agglutinated both untreated and trypsin-treated rabbit erythrocytes and did not agglutinate human blood cells of groups A, B, and O. The gel filtration showed the native molecular mass of 72 kDa and subunit molecular masses of 17 and 18.5 kDa on 12% SDS-PAGE. The lectin activity was inhibited by D-mannose. The tetrameric protein revealed a unique characteristic by forming a broad zone of protein in native PAGE at pH 8.3, which dissociated into seven subunits of varying e/m ratios on acid gel at pH 4.3. These seven bands revealed two polypeptide species of molecular masses 17 and 18.5 kDa on 12% SDS-PAGE, as in the case of the native protein. The result indicated that of the seven subunits, three were homotetramers of 17 kDa, one was a homotetramer of 18.5 kDa, and three were heterotetramers of 17 and 18.5 kDa. The lectin was thermostable with broad pH optima (pH 4-8) and had no requirement for divalent metal cations for its activity. The amino acid composition showed that the lectin contained higher amounts of glycine, alanine, and lysine, but no methionine. The sugar content was estimated to be 5.3% mannose equivalent. The HTTL was mitogenic to mouse spleen (total) cells at 25 microg/ml concentration. The lectin showed characteristics different from those of the earlier reported H. tuberosus tuber lectins and hence opens up a new avenue to investigate the structure-function relationship of lectin in Helianthus species.     

短裙竹荪(Dityophora duplicata)凝集素纯化与生化性质

短裙竹荪子实体经生理盐水抽提、硫酸铵沉淀、DEAE Sepharose和SephadexG 10 0柱层析纯化得到短裙竹荪凝集素 (Dityophoraduplicata(Bosc)Fischerlectin) ,简称DDFL .DDFL经PAGE显示单一条带 ,SDS PAGE测得其亚基分子量为 2 2 3kD ,SephadexG 10 0凝胶过滤测得分子量为 4 5 3kD ,DDFL不含中性糖 ,IEF测得其等电点为 3 92 .该凝集素对供试的 4种血型人血和兔、小牛、鸭、鸡、鲫鱼以及青蛙血红细胞具有凝集作用 ,但不凝集鳖红细胞 .它还可以凝集小鼠脾脏淋巴细胞和小鼠S180 肉瘤细胞 ,对兔红细胞的凝集作用可被乳糖、棉子糖、半乳糖、α 甲基半乳糖、β 甲基半乳糖和N 乙酰半乳糖胺所抑制 .氨基酸组成分析表明 ,DDFL含有 17种氨基酸 ,其中天冬氨酸、丝氨酸、苯丙氨酸和丙氨酸含量较高 .经测定 ,其N末端为甘氨酸 .DDFL对热、酸和碱具有一定的稳定性 ,经 6 0℃处理 10min ,可保持较高的活性 ,在pH 4 0～ 9 0范围内较稳定 ,其凝血活性依赖于Mg2 + 和Ca2 + 二价阳离子 ,Mn2 + 和Zn2 + 则无影响 .DDFL对小鼠腹腔注射的半致死量为 70 6 3mg kg .     

Purification and some characteristics of a beta-galactoside binding soluble lectin from amphibian ovary

Soluble extracts of Bufo ovaries agglutinate sialidase-treated rabbit erythrocytes. Unlike other amphibian lectins this agglutination activity does not require the presence of calcium ions. It is specifically inhibited by D-galactose and its derivatives. Thiodi-D-galactoside is the most potent saccharide inhibitor followed by lactose and methyl-beta-D-galactoside, respectively. D-Fucose, D-glucose and D-mannose do not inhibit the activity at concentrations at or above 100 mM. The lectin has been purified 500-fold to apparent homogeneity from the ovaries by salt extraction and affinity chromatography on lactose-aminophenyl-agarose, with a yield of about 0.2%. The molecular mass determined by gel filtration under native conditions was 30 kDa; polyacrylamide gel electrophoresis in SDS gave a molecular mass of 15 kDa, suggesting that the lectin is a dimer. The lectin has an isoelectric point of 40 and contains a high proportion of acidic amino acids.