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PubMed1986

The binding of fucose-containing glycoproteins by hepatic lectins. Re-examination of the clearance from blood and the binding to membrane receptors and pure lectins.

The nature of the hepatic receptors that bind glycoproteins through fucose at the non-reducing termini of oligosaccharides in glycoproteins has been examined by three different approaches. First, the clearance from blood of intravenously injected glycoproteins was examined in mice with the aid of neoglycoproteins of bovine serum albumin (BSA). The clearance of fucosyl-BSA was rapid and was not strongly inhibited by glycoproteins that inhibit clearance mediated by the galactose or the mannose/N-acetylglucosamine receptors of liver. The clearance of Fuc alpha 1,3(Gal beta 1,4)GlcNAc-BSA (where Fuc is fucose) was inhibited weakly by either Fuc-BSA or Gal beta 1,4GlcNAc-BSA but strongly by a mixture of the two neoglycoproteins, suggesting that its clearance was mediated by hepatic galactose receptors as well as by a fucose-binding receptor. Second, the binding of neoglycoproteins to a membrane fraction of mouse liver was examined. Fuc-BSA binding to membranes was Ca2+ dependent but was not inhibited by glycoproteins that would inhibit the galactose or the mannose/N-acetylglucosamine receptors. In addition, the binding of Fuc-BSA and Gal beta 1,4GlcNAc-BSA differed as a function of pH, in accord with binding of Fuc-BSA through fucose-specific hepatic receptors. Finally, the binding of neoglycoproteins to the pure galactose lectin from rat liver was examined. Neither Fuc-BSA nor Fuc alpha 1,2Gal beta 1,4GlcNAc-BSA bound the galactose lectin, although Fuc alpha 1,3(Gal beta-1,4) GlcNAc-BSA bound avidly. Taken together, these studies suggest that a fucose-binding receptor that differs from the galactose and the mannose/N-acetylglucosamine receptors may exist in rat and mouse liver.

Animals↗

PubMed1978

Studies on lectins. XXXIV. The effect of thermal treatment on the lectin of lentil seeds (Lens esuclenta Moench).

The lectin of lentil seeds (Lens esculenta Moench) dissociates into subunits upon incubation of its solution at temperatures above 50 degrees C. The dissociation is accompanied by precipitation of the heavy subunit, release of Mn2+ from the protein molecule and an almost complete loss of erythroagglutinating activity. Addition of Mn2+ or D-glucose to the lectin solutions has a partially protective effect on the dissociation and inactivation.

Glucose↗

PubMed1994

Conserved waters in legume lectin crystal structures. The importance of bound water for the sequence-structure relationship within the legume lectin family.

An analysis of the water structure in the crystals of different legume lectins has been carried out. Protein hydration is found to be mainly dependent on the detailed local surface characteristics of the protein and will adapt upon the limited conformational changes that are the resultant of crystal packing forces and point mutations. Yet a significant portion of the water positions determined by x-ray crystallography appears to be conserved in all independent crystal structures of a given protein. Some of these waters are specific to this one specific protein, while others are conserved in crystal structures of homologous proteins as well. For those conserved waters, a clear structural role is often evident. Seven water sites were found to be completely conserved in all legume lectin crystal structures, independent of their degree of sequence homology or carbohydrate specificity. Of these, four waters are ligands to the manganese and calcium ions, and one water is located in the saccharide binding site interacting with a conserved Asp and Asn residue. Of the remaining two conserved waters, one of them stabilizes a beta-hairpin, while the other interacts with a beta-bulge structure of the back sheet.

Amino Acid Sequence↗

PubMedDate not supplied

Comparative studies of the interaction between lectins and Leishmania in agglutination tests and enzyme-linked lectin-biotin assays (ELLBA).

It was demonstrated that soybean agglutinin and peanut agglutinin aggregated all the investigated species of Leishmania, including virulent and avirulent members of L. major in agglutination tests. Concanavalin A and Pisum sativum agglutinin were shown to aggregate L. species ZMA and L. major but showed no effect on L. gymnodactyli and L. mexicana amazonensis which were aggregated by wheat germ agglutinin, an extract from Ulex europaeus and Ricinus communis. There was no correlation between the results of ELLBA studied in agglutination tests. The results indicate that the surfaces of Leishmania strains and species are heterogeneous with respect to lectin binding. There are possibly two subsets of lectin receptors on the surface structures of Leishmania cells.

Agglutination Tests↗

PubMed1997

Role of aromatic amino acids in carbohydrate binding of plant lectins: laser photo chemically induced dynamic nuclear polarization study of hevein domain-containing lectins.

Carbohydrate recognition by lectins often involves the side chains of tyrosine, tryptophan, and histidine residues. These moieties are able to produce chemically induced dynamic nuclear polarization (CIDNP) signals after laser irradiation in the presence of a suitable radical pair-generating dye. Elicitation of such a response in proteins implies accessibility of the respective groups to the light-absorbing dye. In principle, this technique is suitable to monitor surface properties of a receptor and the effect of ligand binding if CIDNP-reactive amino acids are affected. The application of this method in glycosciences can provide insights into the protein-carbohydrate interaction process, as illustrated in this initial study. It focuses on a series of N-acetylglucosamine-binding plant lectins of increasing structural complexity (hevein, pseudohevein, Urtica dioica agglutinin and wheat germ agglutinin and its domain B), for which structural NMR- or X-ray crystallographic data permit a decision of the validity of the CIDNP method-derived conclusions. On the other hand, the CIDNP data presented in this study can be used for a rating of our molecular models of hevein, pseudohevein, and domain B obtained by various modeling techniques. Experimentally, the shape and intensity of CIDNP signals are determined in the absence and in the presence of specific glycoligands. When the carbohydrate ligand is bound, CIDNP signals of side chain protons of tyrosine, tryptophan, or histidine residues are altered, for example, they are broadened and of reduced intensity or disappear completely. In the case of UDA, the appearance of a new tryptophan signal upon ligand binding was interpreted as an indication for a conformational change of the corresponding indole ring. Therefore, CIDNP represents a suitable tool to study protein-carbohydrate interactions in solution, complementing methods such as X-ray crystallography, high-resolution multidimensional nuclear magnetic resonance, transferred nuclear Overhauser effect experiments, and molecular modeling.

Amino Acids↗

PubMed1989

Lectin histochemistry of the embryonic heart: fucose-specific lectin binding sites in developing rats and chicks.

Glycoconjugates, particularly their sugar side chains, play important roles in embryonic development. Changes in cell-surface-associated glycoconjugates are known to affect cell differentiation, cellular interactions, and other developmental phenomena during embryogenesis. The embryonic heart goes through a series of complicated morphologic events during development. Of particular interest is morphogenesis of the outflow tract. This region of the embryonic heart originates from more than one cell population and undergoes a complex process of septation during formation of the great vessels. Histochemical analysis with a series of fucose-specific lectins conjugated to horseradish peroxidase has revealed the presence of a fucosylated glycoconjugate in the outflow tract of the developing heart. The results reveal further that the expression of the fucosylated glycoconjugate is stage-dependent and thus probably genetically regulated. The timing and distribution of staining with the lectin OFA suggest that this fucosylated glycoconjugate may play a role in directing the migration of neural crest cells into the heart and subsequent formation of the conus septum.

Animals↗

PubMed2007

Genetic influences on mannan-binding lectin (MBL) and mannan-binding lectin associated serine protease-2 (MASP-2) activity.

The lectin pathway of the complement system is activated when Mannan-binding lectin (MBL) in complex with MASP-2 binds microorganisms. Polymorphisms in both genes are responsible for low serum levels, which associate with increased risk of infection and autoimmune disease. The present study includes 1215 MBL measurements and 1214 MASP-2 activity measurements in healthy Danish adult twins. Total MASP-2 activity was estimated by C4 cleaving activity of samples diluted in an excess of MBL. Twin-twin correlations were higher in monozygotic (MZ) than in dizygotic (DZ) twins for both traits. Heritabilites of MBL levels and MASP-2 activity were estimated using structural equation modeling allowing assessment of the contribution of common genes affecting both traits. The estimated heritability was 0.77 [95% CI 0.64;0.91] for MBL levels and 0.75 [95% CI 0.59;0.81] for MASP-2 activity with the presence of additive genetic factors, shared environmental factors, and non-shared environmental factors. The genetic correlation, i.e., common genetic factors affecting MBL and MASP-2 activity was estimated to r(g) = 0.34 [0.25;0.42]. The data indicate a strong genetic influence for the serum levels of MBL and for MASP-2 activity with a significant genetic correlation between the two traits.

Adult↗

PubMed2006

Towards functional glycomics by localization of binding sites for tissue lectins: lectin histochemical reactivity for galectins during diethylstilbestrol-induced kidney tumorigenesis in male Syrian hamster.

Endogenous lectins act as effectors of cellular activities such as growth regulation, migration, and adhesion. Following their immunohistochemical localization in our previous study (Saussez et al. in Histochem Cell Biol 123:29-41, 2005) we purified several galectins and used them as tools for monitoring accessible binding sites. Herein, we report the use of galectin histochemistry for the analysis of diethylstilbestrol (DES)-induced renal tumors in male Syrian hamster kidney (SHKT). Sections of normal kidney and DES-treated kidney were analyzed with biotinylated galectins-1, -3 (full-length and truncated), and -7. Accessible binding sites were detected, localization was predominantly extracellular and confined to medium-sized and large tumors. Monitoring the SHKT-derived HKT-1097 line, processed in vitro or as xenograft material, cytoplasmic and nuclear staining for galectins-1, -3, and -3tr could be observed. Adaptation of SHKT cells to long-term growth in culture is thus associated with emergence of this signal. Our data set illustrates the feasibility to complement immunohistochemical data by application of the tissue lectins as probes, and to detect regulation of galectin reactivity with differential characteristics within tumor progression in vivo and unique features of the tumor cell line in vitro and in vivo.

Animals↗

PubMed1983

Lectin receptors in the cockroach neuromuscular system. II. Effects of denervation on muscle lectin receptors.

The binding of fluorescent derivatives of plant lectins to the 6 coxal depressor muscles in the leg of the cockroach was examined at 1, 2, 3 and 5 weeks after denervation. Histochemical analysis of the binding of the lectins to frozen sections of the muscles demonstrated that all detectable binding was to the surfaces of the muscle fibers. In addition, within one week of denervation those muscles which in the innervated state have different amounts of D-galactose and/or alpha-N-acetylgalactosamine on their surfaces, now all have identical amounts of these carbohydrates. Biochemical analysis of concanavalin A and wheat germ agglutinin glycoprotein receptors by sodium dodecylsulphate polyacrylamide gel electrophoresis indicated that approximately 17% of all the receptors detected altered their relative levels in denervated muscles. These changes were observed in those receptors that were present in equal amounts in each of the muscles as well as in those receptors that were distributed among the 6 muscles in a manner that correlated with innervation by an identified motor neuron. However, in spite of these changes that reduced the biochemical differences in the denervated CDMs it was still possible to distinguish among the 6 muscles by the nature of the Con A and WGA glycoprotein receptors. Denervated muscles still present biochemically different cell surfaces to regenerating motor neurons.

Animals↗

PubMed1978

Studies on lectins. XXXV. Water-soluble O-glycosyl polyacrylamide derivatives for specific precipitation of lectins.

By copolymerization of acrylamide and allyl glycosides of various sugars, O-glycosyl derivatives of polyacrylamide copolymers were prepared. The sugar content of the copolymers can be varied in the range 0--40%, their sedimentation coefficient shows the vales of 2.5-5.7 S; the molecular weight of an O-alpha-D-mannopyranosyl polyacrylamide copolymer (29% mannose, so20,w = 2.9 S) was estimated as 44 500. Copolymers with incorporated glycosyl residues interacting specifically with lectins yield precipitates with them upon immunodiffusion in cellulose acetate. The quantitative precipitin curves obtained with these copolymers are similar to those produced by quantitative precipitation of lectins with natural polysaccharides. The copolymers may serve as model substances of natural polysaccharides.

Acrylamides↗

PubMed1994

A new mannan-binding lectin from the serum of the eel (Anguilla anguilla L.): isolation, characterization and comparison with the fucose-specific serum lectin.

A new mannan-binding lectin (MBL) and a previously described fucose-binding lectin (FBL) have been isolated from serum of Anguilla anguilla by affinity chromatography on A-peptone-Sepharose in combination with electroelution (MBL) or affinity chromatography using alpha-L-fucose-agarose (FBL). MBL has a mol. wt of approximately 246,000 and is composed of identical subunits of approximately 24,000, two of each are always covalently linked. FBL has a mol. wt of about 121,000 and consists of four subunits of 30,000, which, upon reduction are split into two identical subunits of 15,000. Upon isoelectric focusing MBL displays four bands ranging from pH 4.8 to 5.2. FBL shows 17-20 bands between pH 5.5 and 6.2. Of the inhibitors utilized, hemagglutination activity of MBL is inhibited only by mannan, whereas FBL activity is inhibited by several glycosubstances. MBL and FBL activity is constant between pH 4 and 10 and 5 and 10, respectively. Temperatures above 55 degrees C totally destroy MBL activity whereas FBL activity remains constant up to 75 degrees C.

Anguilla↗

PubMed2006

The mannan-binding lectin pathway and lung disease in cystic fibrosis--disfunction of mannan-binding lectin-associated serine protease 2 (MASP-2) may be a major modifier.

The lectin pathway of complement activation is initiated by mannan-binding lectin (MBL) or the ficolins through the common MBL-associated serine protease-2 (MASP-2). Deficiency of MBL has been associated with poorer outcome in cystic fibrosis (CF). We investigated the MBL pathway further by analysis of the MASP-2 deficiency mutation (D105G) as well as MBL-2 genotypes. Concentrations and genotypes of MASP-2 and MBL in 109 CF patients were correlated to lung function and chronic infections. We describe the first CF patient homozygous for the mutation, a girl with extremely severe lung disease with no other precipitating factors. We suspect total MASP-2 dysfunction to be a major modifier of CF lung disease. However, heterozygosity for the D105G mutation of MASP-2 had no correlation to MBL pathway function or poor lung function. Lung function was higher in the MBL deficiency determining genotypes (XA/YO+YO/YO) than in the other genotypes.

Adolescent↗

PubMed1999

Primary structure of hemolytic lectin CEL-III from marine invertebrate Cucumaria echinata and its cDNA: structural similarity to the B-chain from plant lectin, ricin.

CEL-III, a galactose/N-acetylgalactosamine (Gal/GalNAc) specific lectin purified from a marine invertebrate Cucumaria echinata has a strong hemolytic activity especially toward human and rabbit erythrocytes. We determined the primary structure of the CEL-III by examining the amino acid sequences of the protein and the nucleotide sequence of the cDNA. The cDNA encoding CEL-III has 1823 nucleotides and an open reading frame of 1296 nucleotides. CEL-III is composed of 432 amino acid residues with a M(r) of 47¿ omitted¿457 and has six internal tandem repeats, each with of 40-50 amino acids, comprising the N-terminal two-thirds of the molecule. Similar repeats are found in the B-chains of cytotoxic plant lectins, such as ricin and abrin, where six repetitive sequences extend throughout the molecules. A hydropathy plot predicts hydrophobic segments in the C-terminal region of CEL-III. These findings suggest that the N-terminal region of CEL-III plays an important role in binding to carbohydrate receptors on the target cell membranes, an event which triggers an intermolecular hydrophobic interaction of the C-terminal region, the result being oligomerization of CEL-III to lead to pore-formation in erythrocyte membrane.

Abrin↗

PubMed2002

Calcium modulates protease resistance and carbohydrate binding of a plant defense legume lectin, Griffonia simplicifolia lectin II (GSII).

Site-directed mutagenesis previously identified the residues responsible for the biological activity of the plant defense legume lectin, Griffonia simplicifolia lectin II (GSII) [Proc. Natl. Acad. Sci. USA 95, (1998) 15123-15128]. However, these results were inconclusive as to whether these residues function as direct defense determinants through carbohydrate binding, or whether substantial changes of the protein structure had occurred in mutated proteins, with this structural disruption actually causing the loss of biochemical and biological functions. Evidence shown here supports the former explanation: circular dichroism and fluorescence spectra showed that mutations at carbohydrate-binding residues of GSII do not render it dysfunctional because of substantial secondary or tertiary structure modifications; and trypsin treatment confirmed that rGSII structural integrity is retained in these mutants. Reduced biochemical stability was observed through papain digestion and urea denaturation in mutant versions that had lost carbohydrate-binding ability, and this was correlated with lower Ca(2+) content. Accordingly, the re-addition of Ca(2+) to demetalized proteins could recover resistance to papain in the carbohydrate-binding mutant, but not in the non-binding mutant. Thus, both carbohydrate binding (presumably to targets in the insect gut) and biochemical stability to proteolytic degradation in situ indeed contribute to anti-insect activity, and these activities are Ca(2+)-dependent.

Animals↗

PubMedDate not supplied

Persubstituted cyclodextrin-based glycoclusters as inhibitors of protein-carbohydrate recognition using purified plant and mammalian lectins and wild-type and lectin-gene-transfected tumor cells as targets.

Multivalent glycoclusters have the potential to become pharmaceuticals by virtue of their target specificity toward clinically relevant sugar receptors. Their application can also provide fundamental insights into the impact of two spatial factors on binding, i.e., topologies of ligand (branching mode, cluster presentation) and carbohydrate recognition domains in lectins. Persubstituted macrocycles derived from nucleophilic substitution of iodide from heptakis 6-deoxy-6-iodo-beta-cyclodextrin by the unprotected sodium thiolate of 3-(3-thioacetyl propionamido)propyl glycosides (galactose, lactose and N-acetyllactosamine) were prepared. The produced glycoclusters were first tested as competitive inhibitors in solid-phase assays. A plant toxin from mistletoe and an immunoglobulin G fraction from human serum were markedly susceptible. A nearly 400-fold increase in inhibitory potency of each galactose moiety in the heptavalent form relative to free lactose (217-fold relative to free galactose) was detected. Thus, these glycoclusters can efficiently interfere, for example, with xenoantigen-dependent hyperacute rejection. Among the tested galectins selected from this family of adhesion- and growth-regulatory endogenous lectins, the substituted beta-cyclodextrins acted as sensors to delineate topological differences between the two dimeric prototype proteins. The relatively strong reactivity with chimera-type galectin-3, a mediator of tumor metastasis, disclosed selectivity for glycocluster binding among galectins. Equally important, the geometry of ligand display (maxiclusters, bi- or triantennary N-glycans) made its mark on the inhibitory potency. To further determine the sensitivity of a distinct galectin presented on the cell surface and not in solution, we established a stably transfected tumor cell clone. We detected a significant response to presence of the multivalent inhibitor. This type of chemical scaffold with favorable pharmacologic properties might thus be exploited for the design of galectin- and ligand-type-selective glycoclusters.

Animals↗

PubMed2004

Mistletoe lectin I is a sialic acid-specific lectin with strict preference to gangliosides and glycoproteins with terminal Neu5Ac alpha 2-6Gal beta 1-4GlcNAc residues.

Mistletoe lectin I (ML-I) is a type II ribosome-inactivating protein, which inhibits the protein biosynthesis at the ribosomal level. ML-I is composed of a catalytically active A-chain with rRNA N-glycosidase activity and a B-chain with carbohydrate binding specificities. Using comparative solid-phase binding assays along with electrospray ionization tandem mass spectrometry, ML-I was shown to preferentially bind to terminally alpha2-6-sialylated neolacto series gangliosides from human granulocytes. IV(6)Neu5Ac-nLc4Cer, VI(6)Neu5Ac-nLc6Cer, and VIII(6)Neu5Ac-nLc8Cer were identified as ML-I receptors, whereas the isomeric alpha2-3-sialylated neolacto series gangliosides were not recognized. Only marginal binding of ML-I to terminal galactose residues of neutral glycosphingolipids with a Galbeta1-4Glc or Galbeta1-4GlcNAc sequence was determined, whereas a distal Galalpha1-4Gal, GalNAcbeta1-3Gal, or GalNAcbeta1-4Gal disaccharide did not bind at all. Among the glycoproteins investigated in Western blot and microwell adsorption assays, only those carrying Neu5Acalpha2-6Galbeta1-4GlcNAc residues, exclusively, predominantly, or even as less abundant constituents in an assembly with Neu5Acalpha2-3Galbeta1-4GlcNAc-terminated glycans, displayed high ML-I binding capacity. From our data we conclude that (i) ML-I has to be considered as a sialic acid- and not a galactose-specific lectin and (ii) neolacto series gangliosides and sialoglycoproteins with type II glycans, which share the Neu5Acalpha2-6Galbeta1-4GlcNAc terminus, are true ML-I receptors. This strict preference might help to explain the immunostimulatory potential of ML-I toward certain leukocyte subpopulations and its therapeutic success as a cytotoxic anticancer drug.

Adsorption↗

PubMed1998

Conformer selection and differential restriction of ligand mobility by a plant lectin--conformational behaviour of Galbeta1-3GlcNAcbeta1-R, Galbeta1-3GalNAcbeta1-R and Galbeta1-2Galbeta1-R' in the free state and complexed with galactoside-specific mistletoe lectin as revealed by random-walk and conformational-clustering molecular-mechanics.

To study conformational parameters of ligands before and after complex formation with the galactoside-binding agglutinin of Viscum album L. (VAA) in solution, combined computer-assisted random walk molecular mechanics (RAMM) calculations extended by conformational clustering analysis (CCA), molecular dynamics (MD) simulations as well as two-dimensional rotating-frame nuclear Overhauser effect (ROE) and two-dimensional nuclear Overhauser effect (NOE) spectroscopy NMR experiments were employed. Derivatives of the naturally occurring disaccharides Galbeta1-3GlcNAcbeta1-R and Galbeta1-3GalNAcbeta1-R as well as of a synthetic high-affinity binding partner, i.e. the disaccharide Galbeta1-2Galbeta1-R', were chosen as ligands in this study. The disaccharides displayed inherent flexibility in the valley of the global minimum between phi/psi combinations of (40 degrees/60 degrees) and (40 degrees/-60 degrees). Calculations of the de-N-acetylated sugars revealed that presence of this group did not markedly influence the distribution of low-energy conformers in the phi, psi, epsilon plot. Occupation of side minima at phi/psi (180 degrees/0 degrees) or (0 degrees/180 degrees) is either unlikely or low according to the results of MD simulations and RAMM calculations extended by CCA. Notably, these side minima define conformations which are not stable during a MD simulation. Transitions to other minima occur already a few picoseconds after the start of the simulation. NMR experiments of the free-state ligand confirmed the validity of the data sets obtained by the calculations. Following the description of the conformational space in the free-state NMR experiments were performed for these disaccharides complexed with VAA. They yielded two interresidual contacts for Galbeta1-3GlcNAcbeta1-R and Galbeta1-2Galbeta1-R'. The ligand conformations in the complex did not deviate markedly from those of a minimum conformation in the free state. One- and two-dimensional transferred nuclear Overhauser enhancement (TRNOE) experiments at different mixing times excluded the influence of spin-diffusion effects. When the NOE build-up curves in the three studied cases were compared, the residual mobility of the penultimate carbohydrate unit of Galbeta1-3GalNAcbeta1-R was observed to be higher than that of the respective hexopyranose unit of the other two bound ligands. Due to the availability of the conformational parameters of Galbeta1-2Galbeta1-R' in association with a galectin, namely the beta-galactoside-binding protein from chicken liver, it is remarkable to note that this ligand displays different conformations in the binding sites of either the plant or the animal lectin. They correspond to local energy-minimum conformations in the phi,psi, epsilon plot and substantiate differential conformer selection by these two lectins with identical nominal monosaccharide specificity.

Binding Sites↗

PubMed2000

Biochemical properties and cDNa cloning of two new lectins from the plasma of Tachypleus tridentatus: Tachypleus plasma lectin 1 and 2+.

A Sepharose CL-4B-binding protein, Tachypleus plasma lectin 1 (TPL-1), and a lipopolysaccharide (LPS)-binding protein, Tachypleus plasma lectin-2 (TPL-2), have been isolated from the plasma of Tachypleus tridentatus and biochemically characterized. Each protein is coded by a homologous family of multigenes. TPL-1 binds to Sepharose CL-4B and was eluted with buffer containing 0.4 m GlcNAc. The deduced amino acid sequence of TPL-1 consisted of 232 amino acids with an N-glycosylation site, Asn-Gly-Ser at residues 74-76. It shares a 65% sequence identity and similar internal repeats of about 20 amino acid motifs with tachylectin-1. Tachylectin-1 was identified as a lipopolysaccharide-agarose binding nonglycosylated protein from the amebocytes of T. tridentatus. TPL-2 was eluted from the LPS-Sepharose CL-4B affinity column in buffer containing 0.4 m GlcNAc and 2 m KCl. The deduced amino acid sequence of TPL-2 consisted of 128 amino acids with an N-glycosylation site, Asn-Cys-Thr, at positions 3-5. It shares an 80% sequence identity with tachylectin-3, isolated from the amebocytes of T. tridentatus. TPL-2 purified by LPS-affinity column from the plasma predominantly exists as a dimer of a glycoprotein with an apparent molecular mass of 36 kDa. Tachylectin-3 is an intracellular nonglycosylated protein that also exists as a dimer in solution with an apparent molecular mass of 29 kDa. It recognizes Gram-negative bacteria through the 0-antigen of LPS. Western blot analyses showed that, in the plasma, TPL-1 and TPL-2 exist predominantly as oligomers with molecular masses above 60 kDa. They both bind to Gram-positive and Gram-negative bacteria, and this binding is inhibited by GlcNAc. Possible binding site of TPL-1 and TPL-2 to the bacteria could be at the NAc moiety of GlcNAc-MurNAc of the peptidoglycan. The physiological function of TPL-1 and TPL-2 is most likely related to their ability to form a cluster of interlocking molecules to immobilize and entrap invading organisms.

Amino Acid Sequence↗