Effect of pea and lentil lectins on in vitro absorption of nutrients

In vitro absorption of nutrients like glucose, leucine, protein hydrolysate and Ca2+ by ligated loops of small intestine was significantly affected in presence of lectins from peas and lentils. Except for sucrose, all other nutrients showed significant decrease in their absorption in presence of lectins. Lentil lectins had a greater inhibitory effect than pea lectins.     

Nuclear magnetic resonance investigation of cadmium 113 substituted pea and lentil lectins

The lentil (LcH) and pea (PSA) lectins, which are members of the class of D-glucose/D-mannose binding lectins, are Ca2+ X Mn2+ metalloproteins that require the metal ions for their saccharide binding and biological activities. We have prepared a variety of Cd2+ derivatives of PSA and LcH, with Cd2+ in either the transition metal (S1) or calcium (S2) sites, or in both. Thus, Cd2+ X Zn2+, Cd2+ X Mn2+, and Ca2+ X Cd2+ derivatives were prepared, in addition to the Cd2+ X Cd2+ derivatives which we have recently reported. This is the first report of stable mixed metal Cd2+ complexes of lectins. The physical and saccharide binding properties of the Cd2+ derivatives of both lectins were characterized by a variety of physiochemical techniques and found to be the same as those of the corresponding native proteins. 113Cd NMR spectra of mono- and disubstituted 113Cd2+ complexes of LcH and PSA were recorded and compared with 113Cd NMR data for concanavalin A (ConA) (Palmer, A.R., Bailey, D.B., Behnke, W.D., Cardin, A.D., Yang, P.P., and Ellis, P.D. (1980) Biochemistry 19, 5063-5070). The data for the PSA and LcH derivatives were found to be very similar, indicating close homology of their metal ion binding sites. 113Cd resonances at 44.6 ppm and -129.4 ppm for 113Cd2+ X 113Cd2+ X LcH, and at 46.6 and -130.4 for the corresponding PSA derivative, are chemical shifts very similar to those observed for 113Cd2+ X 113Cd2+ X ConA. Assignment of the resonances to the transition metal (S1) and calcium (S2) sites were unambiguous since the Ca2+ X 113Cd2+ and 113Cd2+ X Zn2+ derivatives of both lectins showed single resonances characteristic of the S1 and S2 sites, respectively. The results indicate that, unlike ConA, 113Cd2+ binds tightly to PSA and LcH. Binding of monosaccharide to both lectins induce small (2 ppm) upfield shifts in their S2 113Cd resonances, in contrast to the larger shift (8 ppm) observed in ConA. The 113Cd2+ X Mn2+ complexes of PSA and LcH fail to show a 113Cd resonance characteristic of these derivatives, which provides evidence for the close proximity of the metal ions in the two proteins. The present findings indicate that the coordinating ligand atoms to the metal ions at the S1 and S2 sites in LcH, PSA, and ConA are the same.     

Preparation and properties of metal ion derivatives of the lentil and pea lectins

Lentil lectin (LcH) and pea lectin (PSA) belong to the class of D-glucose/D-mannose binding lectins and resemble concanavalin A (Con A) closely in physicochemical, structural, and biological properties. LcH and PSA, like Con A, are Ca2+-Mn2+ metalloproteins that require the metal ions for their saccharide binding and biological activities. Studies of the relationship between the metal ions binding and saccharide binding activity in LcH and PSA have been difficult due to the problem of metal ion replacement in these proteins. We now report a method of metal ion replacement in both lectins that allows substitution of the Mn2+ in the native proteins with a variety of transition metal ions, as well as substitution of the Ca2+ with Cd2+ in a particular complex. The following metal ion derivatives of both LcH and PSA have been prepared: Ca2+-Zn2+, Ca2+-Co2+, Ca2+-Ni2+, and Cd2+-Cd2+. All of these derivatives are as active as the native lectins, as demonstrated by precipitation with specific polysaccharides, saccharide inhibition of precipitation, and hemagglutination assays. The yields of these derivatives are good (generally greater than 70%), and the degree of metal ion incorporation is high (generally greater than 90%). The method of preparation is quite different from that for metal ion substitution in Con A, which proceeds via the apoprotein. In contrast, the apoproteins of LcH and PSA are unstable, aggregate above pH 4.0, and cannot be remetallized once formed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intraperitoneal toxicity of pea and lentil lectins in albino rats--effect on growth and osmotic fragility of erythrocytes

Lectins from peas and lentils when injected to rats apparently appeared to be non toxic but they caused growth depression. The organ weights were not affected except spleen enlargement. The lectins also caused increased osmotic fragility of erythrocytes without affecting other hematological parameters such as haemoglobin, packed cell volume, and RBC count.     

Binding of p-substituted-phenyl glycosides to the lectins from the pea and the lentil

The effect of p-substitution on the behaviour of phenyl α-D-mannopyranosides as specific ligands for the lectins from Pisum sativum (pea) and Lens culinaris (lentil) is reported. The binding affinities are related to the electronic properties of the substituents, expressed as the Hammett substituent constant (p = ?0.4). Inductive and mesomeric contributions are best considered separately. Neither steric hindrance nor hydrophobic binding of the substituents is observed. For the binding of the corresponding α-D-glucopyranosides to the Pisum sativum lectin, the same effect is maintained (p = ?0.4). In a series of p-substituted-phenyl β-D-glucopyranosides, the nature of the substituent has almost no effect on the binding to the Pisum sativum lectin.     

IGF-II binding on human lymphoid cells: demonstration of a common high affinity receptor for insulin like peptides

We have studied the binding of 125I-GF-II to the IM-9 human lymphoid cell line, and to human placental membranes. All of IGF-II radioligand binding to IM-9 cells, and half of the binding to human placental membranes is to a previously unrecognized common (Type-III) high affinity receptor site for insulin-like peptides, in which IGF-I and IGF-II are equipotent and insulin only slightly less potent. This common receptor represents another mechanism by which insulin, and the somatomedins can exert biological action.     

Receptors for antigen on lymphoid cells. II. The nature of the molecule responsible for plaque-forming cell adherence.

The nature of specific adherence of rat anti-TNP PFC to TNP-GRBC has been investigated with PLL-fixed antigen monolayers as cellular immunoadsorbents and as plaque indicators. The immunoglobulin nature of the molecule responsible for PFC adherence is suggested by the fact that pretreatment of the PFC with rabbit anti-rat Ig antisera, but not anti-histocompatibility antisera, inhibits adherence. Removal of the adherence capacity of early PFC with the proteolytic enzymes papain and pronase, or by "capping" with anti-Ig is followed by slow regeneration of the ability to adhere, suggesting that adherence is due to membrane rather than secreted immunoglobulin, the latter being detectable within minutes after enzyme treatment. Several time-related events relating to PFC adherence were observed. 1) Both direct and indirect PFC are capable of specific adherence; the ability to adhere, however, tends to decline with time, especially after secondary immunization. 2) Although early PFC adherence is unaffected by trypsin treatment, later populations become increasingly sensitive. 3) Pretreatment of PFC at various times after primary immunization with antisera specific for rat mu-chain indicates that IgM and possibly early IgG-secreting PFC have mu heavy chains on their surface. These data suggest that the PFC membrane is progressively changing during the maturation of the antibody response.     

Correspondence between lectin-defined and surface antigen-defined cell subpopulations in the human thymus: its variation during ontogeny

In the thymus of children, congruent to 50% of cells are recognized both by peanut agglutinin and soybean agglutinin (PNA+, SBA+), congruent to 23% of cells are PNA-, SBA-, and 23% are PNA-, SBA+. This pattern of recognition was compared with the reactivity of these cells with monoclonal antibodies recognizing T cell differentiation antigens A 50 and a series (T3, T6, T8) that defines 3 discrete stages of T cell differentiation. Most PNA+, SBA+ display T6 and T8 but not T3 antigens; most PNA-, SBA+ display T3+ and A 50+ but not T6; and T3-, T6-, A 50- cells are PNA-, SBA-. Thus, there is a close correspondence between PNA+, SBA+ cells and the common (cortical) T3-, T6+ thymocytes; between PNA-, SBA+ cells and late (medullary) T3+, T6- thymocytes; and between PNA-, SBA- cells and early thymocytes. During ontogeny, although there are fewer PNA+ cells in the thymus, the proportion of T3+ cells, T6+ cells, and T3-, T6- cells showed no major modification as early as 16 wk.     

Circular dichroism and 1H NMR studies of Co2+- and Ni2+-substituted concanavalin A and the lentil and pea lectins

Visible absorption, circular dichroism (CD) and magnetic circular dichroism spectra have been recorded for the Ca2+-Co2+ derivatives of the lentil (CCoLcH) and pea (CCoPSA) lectins (Co2+ at the S1 sites and Ca2+ at the S2 sites) and shown to be very similar for both proteins. The visible absorption and magnetic circular dichroism spectra indicate similar octahedral geometries for high spin Co2+ at S1 in both proteins, as found in the Ca2+-Co2+ complex of concanavalin A (CCoPL) (Richardson, C. E., and Behnke, W. D. (1976) J. Mol. Biol. 102, 441-451). The visible CD data, however, indicate differences in the environment around S1 of CCoLcH and CCoPSA compared to CCoPL. 1H NMR spectra at 90 MHz of the Co2+ and Ni2+ derivatives of the lectins show a number of isotropically shifted signals which arise from protons in the immediate vicinity of the S1 sites. Analysis of the spectra of the Co2+ derivatives in H2O and D2O has permitted resonance assignments of the side chain ring protons of the coordinated histidine at S1 in the lectins. Differences are observed in the H-D exchange rate of the histidine NH proton at S1 in concanavalin A compared to the lentil and pea lectins. NMR data of the Ni2+-substituted proteins, together with spectra of the Co2+ derivatives, also indicate that the side chains of a carboxylate ligand and of the histidine residue at S1 are positioned differently in concanavalin A than in the other two lectins. These results appear to account, in part, for the differences observed in the visible CD spectra of the Co2+-substituted proteins. In addition, binding of monosaccharides does not significantly perturb the spectra of the lectins. An unusual feature in the 1H NMR spectra of all three Co2+-substituted lectins is the presence of two exchangeable downfield shifted resonances which appear to be associated with the two protons of a slowly exchanging water molecule coordinated to the Ca2+ ion at S2. T1 measurements of CCoLcH have provided an estimation of the distances from the Co2+ ion to these two protons of 3.7 and 4.0 A.     

Binding of lectins to human leukaemic cells

The interactions of five different lectins: peanut (PNA), lentil (LEN), wheat germ (WGA), soybean (SBA), Asparagus pea (FBP) with leukaemic cells obtained from 31 children: 25 with acute lymphoblastic leukaemia (ALL) and 6 with acute myeloblastic leukaemia (AML) were examined in this study. The relationship of lectin-binding ability to cells cytomorphological, cytochemical and immunological features and its potential clinical application were investigated. It has been shown that PNA and LEN receptors were found in the majority of blast cells. The SBA reacting cells were found only in few patients and FBP binding was not found in studied ALL and AML cells. There was a clear difference in the WGA binding capacity in ALL cells with L1 and L2 characteristics respectively. No differences were found in PNA. WGA and LEN reactivity between PAS negative and PAS positive leukaemic cells. Only PNA of all studied lectins seemed to differentiate T- from B-ALL blast cells. Only WGA binding of ALL cells showed the positive correlation to the risk index value.     

Characterization and biological implications of membrane lectins in tumor, lymphoid and myeloid cells

Complex carbohydrates and sugar receptors at the surface of eukaryotic cells are involved in recognition phenomena. Membrane lectins have been characterized, using biochemical, biological and cytological methods. Their biological activities have been assessed using labeled glycoproteins or neoglycoproteins. Specific glycoproteins or neoglycoproteins have been used to inhibit their binding capacity in both in vitro and in vivo experiments. In adults, lymphoid and myeloid cells as well as tumor cells grow in a given organ and eventually migrate and home in another organ; these phenomena are known as the homing process or metastasis, respectively. In specific cases, membrane lectins of endothelial cells recognize cell surface glycoconjugates of lymphocytes or tumor cells, while membrane lectins of lymphocytes and of tumor cells recognize glycoconjugates of extracellular matrices or of non-migrating cells. Therefore, membrane lectins are involved in cell-cell recognition phenomena. Membrane lectins are also involved in endocytosis and intracellular traffic of glycoconjugates. This property has been demonstrated not only in hepatocytes, fibroblasts, macrophages and histiocytes but also in tumor cells, monocytes, thyrocytes, etc. Upon endocytosis, membrane lectins are present in endosomes, whose luminal pH rapidly decreases. In cells such as tumor cells or macrophages, endosomes fuse with lysosomes; it is therefore possible to target cytotoxic drugs or activators, by binding them to specific glycoconjugates or neoglycoproteins through a linkage specifically hydrolyzed by lysosomal enzymes. In cells such as monocytes, the delivery of glycoconjugates to lysosomes is not active; in this case, it would be preferable to use an acid-labile linkage. Cell surface membrane lectins are developmentally regulated; they are present at given stages of differentiation and of malignant transformation. Cell surface membrane lectins usually bind glycoconjugates at neutral pH but not in acidic medium: their ligand is released in acidic specialized organelles; the internalized ligand may be then delivered into lysosomes, while the membrane lectin is recycled. Some membrane lectins, however, do bind their ligand in relatively acidic medium as in the case of thyrocytes. The presence of cell surface membrane lectins which recognize specific sugar moieties opens the way to interesting applications: for instance, isolation of cell subpopulations such as human suppressor T cells, targeting of anti-tumor or anti-viral drugs, targeting of immunomodulators or biological response modifiers.     

Immunogenicity of human B cell antigens solubilized from cultured human lymphoid cells.

Antigens solubilized from culured human lymphoid cells WI-L2 and RPMI 1788 were partially purified by ultracentrifugation on a KBr gradient. These antigens injected into rabbits produced xenoantibodies which after absorption with melanoma cells became specific to B cell antigens. Three such xenoantisera were submitted to the Second Histocompatibility Workshop of the Americas and reacted much like alloantisera to B cell antigens against a large panel of B peripheral lymphocytes and cells from patients with chronic lymphocytic leukemia. Xenoantisera to B cell antigens inhibited the mixed lymphocyte reaction, but did not affect the mitogenic activity of phytohemagglutinin or the functional properties of C3 receptors, monkey red blood cell receptors, or T cell receptors.     

Post-translational proteolytic processing and the isolectins of lentil and other Viciae seed lectins

Electrospray mass spectrometry was used to identify precisely the proteolytic cleavage points within, and at the C-termini of, the proprotein forms of four Viciae lectins that give rise to their two-chain forms. The lectins examined were the pea and lentil lectins, favin and theLathyrus odoratus lectin, which represent each of the four genera in this tribe. The molecular mass data showed single -chain forms for each lectin, with masses consistent with the available sequence and glycopeptide data, indicating that each came from a single proprotein. In contrast, the pea, lentil andL. odoratus -chains occurred in as many as five forms, due to multiple C-terminal cleavage points. Only favin showed a single -chain form. The -chain mass data were again consistent with the sequence information available, except for the lenti lectin -chain which was re-determined by protein sequencing. The two isolectin forms of this protein were shown to arise from -chain species with and without residue Lys53. The mass spectrum of concanavalin A was also examined and both the single-chain form and the two fragment forms showed no evidence of C-terminal heterogeneity.     

Preparation and characterization of Ca2+-Zn2+-derivatives of lentil and pea lectins and comparison with the native forms

Ca²⁺-Zn²⁺-derivatives of lentil and pea lectins were prepared for the first time by a unique method involving dialysis of the native Ca²⁺-Mn²⁺-lectins against large excesses of metal ions in pH 4.0 buffer. Each derivative contained about 1.5 g atoms of Ca²⁺ and about 1 g atom of Zn²⁺ per monomer. The derivatives were found to be identical to their respective native forms, both in molecular weight and carbohydrate binding activities. Solvent proton relaxation dispersion measurements were used to characterize both the Ca²⁺-Zn²⁺- and Ca²⁺-Mn²⁺-complexes of the lentil lectin.     

Receptors for IgG and complement in human spleen lymphoid cells. Preferential binding of particulate immune complexes through complement receptors.

Human lymphoid spleen cells attached to Petri dishes by poly-L-lysine bind 51Cr-labeled erythrocytes coated with IgG antibodies or complement but not uncoated erythrocytes or those coated with IgM antibodies. The number of erythrocytes bound through complement receptors is several times larger than that bound through IgG receptors. Increasing up to five times the number of IgG molecules on the red blood cells only leads to a slight increase of binding. However, the addition of complement to the IgG-coated erthrocytes increases 10 times the binding to spleen cells, even in the presence of an excess of normal IgG. These results can be explained by postulating that there is a larger number (or greater affinity) of spleen cell receptors for complement than that of spleen cell receptors for IgG.     

A method for the ultrastructural demonstration of non-specific esterase in human blood and lymphoid tissue

Summary Using the substrate 2-naphthylthiol acetate (NTA), we developed a reproducible method of demonstrating a non-specific esterase while retaining nuclear and cytoplasmic details at the ultrastructural level. The NTA esterase had a distribution and pattern of staining similar to those of esterases demonstrable at the light microscopic level by the -naphthyl acetate or naphthol AS-D acetate esterase reaction.The NTA esterase appeared as intensely electron-dense granules of varying size and shape in the cytoplasm. The granules were most abundant in the cells of the histiomonocytic series. The large number of diffusely scattered granules in the cytoplasm of the histiocytes and monocytes made it possible to separate these cells from other haematopoietic elements. There was usually no direct relationship between the NTA esterase positivity and the amount or the location of lysosomes or mitochondria, although in some histoocytes the granules appeared to the associated with lysosomes. The NTA esterase-positive granules were usually more numerous than lysosomes and were located outside the lysosomal granules. Some of the lymphocytes outside the germinal centres and most of the lymphocytes in the blood showed a punctate positivity in the form of 1–4 electron-dense dots. Plasma cells were usually negative but, in rare cases, contained an occasional single dot-like reaction product similar to that in some of the lymphocytes. Granulocytes were always negative.The method described in this paper can be used effectively for identification and study of human haematopoietic cell lines at the ultrastructural level.