The amino-acid sequence of a lectin of the acorn barnacle Megabalanus rosa

Diversified carbohydrate-binding lectins from marine resources

Marine bioresources produce a great variety of specific and potent bioactive molecules including natural organic compounds such as fatty acids, polysaccharides, polyether, peptides, proteins, and enzymes. Lectins are also one of the promising candidates for useful therapeutic agents because they can recognize the specific carbohydrate structures such as proteoglycans, glycoproteins, and glycolipids, resulting in the regulation of various cells via glycoconjugates and their physiological and pathological phenomenon through the host-pathogen interactions and cell-cell communications. Here, we review the multiple lectins from marine resources including fishes and sea invertebrate in terms of their structure-activity relationships and molecular evolution. Especially, we focus on the unique structural properties and molecular evolution of C-type lectins, galectin, F-type lectin, and rhamnose-binding lectin families.

Multiple subfamilies of carbohydrate recognition domains in animal lectins

Calcium ion-dependent carbohydrate recognition domains (CRDs) are found in a range of proteins including receptors for serum glycoproteins and proteoglycans of the extracellular matrix. These C-type CRDs have homologous amino acid sequences characterized by the presence of certain invariant residues. Analysis of the genes for five of the proteins reveals that in each case the CRD-coding sequence is separated from the rest of the gene by an intron. The genes fall into two groups: those in which the coding sequence for the CRD is interrupted by two introns, and those in which the coding sequence is contained in a single exon. The sequences of domains in each category are consistent with the suggestion that the different gene structures reflect early evolutionary divergence of two subfamilies of C-type CRDs in animal lectins. However, carbohydrate-binding specificity does not directly parallel the evolutionary categorization. Comparison of the primary structures of CRDs in each subfamily which have related binding specificities may help to identify residues involved in ligating carbohydrates. This type of analysis is being extended by the use of bacterial expression systems to investigate in greater detail the binding characteristics of the CRDs.

Diverse sugar-binding specificities of marine invertebrate C-type lectins

The sugar-binding specificities of C-type lectins isolated from marine invertebrates were investigated by frontal affinity chromatography (FAC) using 100 oligosaccharides. The lectins included BRA-2 and BRA-3, multiple lectins from the hemolymph of the acorn barnacle, Megabalanus rosa, and BRL from the acorn barnacle, Balanus rostatus. The diverse sugar-binding specificities of the C-type lectins were determined by FAC analysis. BRA-2 recognized alpha2-6 sialylation but not alpha2-3 sialylation on glycans. On the other hand, BRA-3 showed high affinity for oligosaccharides with alpha-linked non-reducing terminal galactose, but not for sialylated forms, and BRL showed enhanced recognition activity towards Lewis(x) and Lewis(a) epitopes.

Isolation, characterization and molecular evolution of a novel pearl shell lectin from a marine bivalve, Pteria penguin

A novel lectin, PPL, was isolated from the mantle of penguin wing oyster (Pteria penguin) by affinity chromatography on mucin-Sepharose 4B and cation exchange chromatography on HiTrap SP. This lectin was estimated to be a 21-kDa monomer by gel filtration, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted time of flight (MALDI-TOF) mass spectrometry. However, dynamic light scattering experiments revealed that a non-covalently linked dimer formed under high salt conditions (500 mM NaCl). Interestingly, PPL showed an increasing hemagglutinating activity with increasing salt concentration. The amino acid sequence of PPL was determined by direct protein sequence analysis and cDNA cloning. The 167-amino acid sequence included 24 lysine residues and had two tandemly repeated homologous domains (residues 20-78 and 107-165) with 44% internal homology. PPL showed sequence homology to L-rhamnose-binding lectins from fish eggs and a D-galactose-binding lectin from sea urchin eggs, with sequence identities in the range 37-48%. PPL agglutinated various animal erythrocytes independently of calcium ions. The minimum concentration of PPL needed to agglutinate rabbit erythrocytes was 0.5 micro g/ml, and the most effective saccharides to inhibit the hemagglutination were D-galactose, methyl-D-galactopyranoside and N-acetyl-D-lactosamine. Lactose also inhibited hemagglutination, but L-rhamnose did so only weakly despite the sequence homology with trout egg L-rhamnose-binding lectins. The carbohydrate-binding specificity of PPL was further examined by frontal affinity chromatography using 37 different pyridylaminated oligosaccharides. PPL was found to have strong binding affinity for various oligosaccharides that have Galbeta1-4Glu/GlcNAc, Galbeta1-3GalNAc/GlcNAc and Galalpha 1-4Gal moieties in their structure. PPL had a high thermal stability and retained 50% of its hemagglutinating activity after incubation at 70 degrees C for 100 min. It agglutinated some Gram-negative bacteria by recognizing lipopolysaccharides. Together, these results suggest that PPL is a new member of the trout egg lectin family which participates in the self-defense mechanism against bacteria and pathogens with a distinct carbohydrate-binding specificity. We conclude that the trout egg lectin family proteins, in particular their carbohydrate recognition domains, have acquired diverse carbohydrate-binding specificities during molecular evolution.

Functional and structural characterization of multiple galectins from the skin mucus of conger eel, Conger myriaster

The complete amino acid sequence of an isogalectin, named congerin II, isolated from the skin mucus of conger eel, was determined by sequencing of the protein and its peptides generated by enzymatic and chemical cleavages. Congerin II consisted of 135 amino acids residues containing an acetylated N-terminus. Congerin II was found to be only 46% homologous in sequence to congerin I which was previously determined (Muramoto K., Kamiya H., Biochem. Biophys. Acta, 1992;1116:129-136), suggesting that the galectins with diverse molecular properties are present in the skin mucus of conger eel. However, it was confirmed by analysis of the secondary structures using circular dichroism that both congerins I and II shared similar folds characterized by beta structures. Congerins I and II showed different molecular properties such as thermostability, pH dependency for hemagglutinating activity and for binding specificity against the pyridylamino derivative of lactose. Congerin I showed more strict recognition specificity for lactose than did congerin II. Furthermore, the effects of chemical modification on congerins I and II were investigated in order to identify the type of amino acids involved in their different lectin activities. Modification of tyrosine and lysine residues did not affect the carbohydrate-binding activities of congerins. However, modification of tryptophan, arginine, histidine, glutamic acid and aspartic acid residues led to considerable loss of their activities, and a different mode of binding activity was observed between modified congerins I and II. These results suggest that multiple galectins from conger eel with the same scaffold have different biological functions and properties.

A unique primary structure, cDNA cloning and function of a galactose-specific lectin from ascidian plasma

The complete amino acid sequence of a galactose-specific lectin from the plasma of the ascidian Halocynthia roretzi has been determined by sequential Edman degradation analysis of peptide fragments derived by proteolytic fragmentation and chemical cleavage of the reductive S-pyridylethylated lectin. Peptide fragments were separated by reverse-phase HPLC. The N-terminal and C-terminal amino acid sequences were determined by Edman degradation and enzymatic digestion. The H. roretzi plasma lectin is a single-chain protein consisting of 327 amino acids and four disulfide bonds, one of which was found to be cross-linked intramolecularly. A comparison of the amino acid sequence of the H. roretzi plasma lectin with the sequences of other proteins reveals that the H. roretzi lectin has a structure consisting of a twice-repeated sequence, a fibrinogen-related sequence and a C-type lectin-homologous sequence. The above amino acid sequence was verified by cDNA cloning of this lectin. Three cDNA clones that have single ORFs encoding the lectin precursor were isolated from an H. roretzi hepatopancreas cDNA library. The deduced amino acid sequences in the three cDNA clones contain the same sequence of the mature lectin molecule and the same putative signal sequence. In addition, it was demonstrated that this lectin can enhance phagocytosis by H. roretzi hemocytes. Thus, the plasma lectin is constructed into an oligomer structure via intermolecular disulfide bonds and plays a role in the biological defense of H. roretzi as a defense molecule.

Purification, characterization, and cDNA cloning of a galactose-specific C-type lectin from Drosophila melanogaster

We purified a lectin from a pupal extract of Drosophila melanogaster. This lectin agglutinated trypsinized and glutaraldehyde-fixed bovine red blood cells in the presence of calcium or magnesium. The hapten sugar of this lectin was galactose. The molecular mass of the intact lectin was determined to be 41 kDa, and it comprised 14- and 17-kDa subunits. The 17-kDa subunit was shown to be a glycosylated form of the 14-kDa subunit. Analysis of the cDNA for this lectin revealed that the 14-kDa subunit consists of 163 amino acid residues and contains all residues conserved in various C-type lectins. It was suggested that the Drosophila lectin and Sarcophaga lectin share some properties and function similarly in defense and development, but probably they are not structural homologues.

Presence of the Periplaneta lectin-related protein family in the American cockroach Periplaneta americana

We determined the partial amino acid sequences of Periplaneta lectin, which we had purified and characterized previously from the hemolymph of the American cockroach (Periplaneta americana) [Kubo T. and Natori S. (1987) Eur. J. Biochem. 168, 75-82]. Based on these sequences, we performed PCR and found that the cDNA library of the Periplaneta fat body contained many similar, but not identical, Periplaneta lectin-related cDNAs. Analysis of the cloned cDNAs suggested that Periplaneta has a protein family, of which the periplaneta lectin and LPS binding protein purified previously are members.

Isolation of a novel lectin from the globiferous pedicellariae of the sea urchin Toxopneustes pileolus

Sea urchin lectin-I (SUL-I), a 32 kDa lectin was purified from the large globiferous pedicellariae of the sea urchin, Toxopneustes pileolus by using gel permeation chromatography, ion-exchange chromatography and reverse-phase HPLC. SDS-PAGE showed that SUL-I is a monomeric protein with a molecular mass of 32 kDa. Amino acid analysis indicates SUL-I to contain 294 residues. SUL-I was shown to have chemotactic properties for guinea-pig neutrophils at concentrations of 0.625 microgram/ml. These data suggest that a 32 kDa lectin from T. pileolus may be related to defensive role.

Comparative modeling of the three-dimensional structure of type II antifreeze protein

Type II antifreeze proteins (AFP), which inhibit the growth of seed ice crystals in the blood of certain fishes (sea raven, herring, and smelt), are the largest known fish AFPs and the only class for which detailed structural information is not yet available. However, a sequence homology has been recognized between these proteins and the carbohydrate recognition domain of C-type lectins. The structure of this domain from rat mannose-binding protein (MBP-A) has been solved by X-ray crystallography (Weis WI, Drickamer K, Hendrickson WA, 1992, Nature 360:127-134) and provided the coordinates for constructing the three-dimensional model of the 129-amino acid Type II AFP from sea raven, to which it shows 19% sequence identity. Multiple sequence alignments between Type II AFPs, pancreatic stone protein, MBP-A, and as many as 50 carbohydrate-recognition domain sequences from various lectins were performed to determine reliably aligned sequence regions. Successive molecular dynamics and energy minimization calculations were used to relax bond lengths and angles and to identify flexible regions. The derived structure contains two alpha-helices, two beta-sheets, and a high proportion of amino acids in loops and turns. The model is in good agreement with preliminary NMR spectroscopic analyses. It explains the observed differences in calcium binding between sea raven Type II AFP and MBP-A. Furthermore, the model proposes the formation of five disulfide bridges between Cys 7 and Cys 18, Cys 35 and Cys 125, Cys 69 and Cys 100, Cys 89 and Cys 111, and Cys 101 and Cys 117.(ABSTRACT TRUNCATED AT 250 WORDS)

A novel role of Periplaneta lectin as an opsonin to recognize 2-keto-3-deoxy octonate residues of bacterial lipopolysaccharides

1. Periplaneta lectin of the American cockroach was shown to have affinity to bacterial lipopolysaccharides (LPS) of chemotypes Rb-Re, but not to lipid A. 2. 2-Keto-3-deoxy octonate (KDO) was the most effective sugar so far tested for inhibition of the hemagglutinating activity of Periplaneta lectin. 3. Periplaneta lectin was suggested to participate in the clearance of bacteria injected into the abdominal cavity of the cockroach.

Acorn barnacle Megabalanus rosa lectin (BRA-3): cDNA cloning, gene structure and seasonal changes of mRNA and protein levels

We have isolated cDNA clones coding for a lectin (BRA-3) from the acorn barnacle, Megabalanus rosa. Sequence comparison of the cDNA clones has revealed polymorphism in the BRA-3 mRNA, which results from single-nucleotide (nt) differences at three positions. All three differences are within the coding region and cause conservative amino acid (aa) changes. The BRA-3 gene is composed of four exons, and the three single-nt differences are located on different exons. In addition, the BRA-3 mRNA and BRA-3 protein levels increased during early summer in a similar fashion, indicating that BRA-3 production is regulated mainly at the level of transcription.

Isolation and characterization of a cDNA clone encoding a Pleurodeles lectin

A cDNA encoding a lectin secreted by the oviduct of Pleurodeles waltl has been isolated and sequenced. The cDNA was identified by comparing the N-terminal amino-acid sequence of the purified P. waltl lectin polypeptides with the amino-acid sequence deduced from the cDNA. The two chains of the mature protein can be encoded within a unique mRNA. Two mRNA were also found in the oviduct extracts. However, they probably result from differential polyadenylation events. The mRNA are strictly localized in the anterior part of the oviduct and increase after estradiol stimulation, two characteristics which have been previously demonstrated for the protein. P. waltl is known to possess a very high DNA content (approximately 2 x 10(10) bp) but the aforementioned results and Southern-blot experiments suggest a unique or at least a very low gene-copy number for this protein. The amino-acid sequence of the P. waltl lectin deduced from the cDNA sequence shows similarities with the C-type carbohydrate-recognition domains of animal lectins as defined by Drickamer [Drickamer, K. (1988) J. Biol. Chem. 263, 9557-9560]. Although it is regulated by estradiol, the P. waltl lectin amino-acid sequence shows a higher similarity with animal lectins involved in the defence of the organism than with those involved in reproduction and development.

Agglutinins from aquatic insects--tumor cell agglutination activity

Agglutinins were identified in whole body extracts of aquatic insects by means of murine tumor cell agglutination, using sarcoma 180 ascites, Ehrlich, and MM-46 cells. Screening revealed agglutinins in 5 of 10 of the larvae tested, and in 2 of 6 of the water-dwelling adult insects; Gerris paludum insularis and Gyrinus japonicus. Only the agglutinin from adult G. paludum also agglutinated human erythrocytes. An ascites tumor was converted into a solid form in vivo after administration of G. paludum agglutinin. The observation that these aquatic insect agglutinins preferentially agglutinate tumor cells has considerable implications in terms of anti-tumor effects such as inhibition of cell proliferation and metastasis.

Comparative investigations on the amino-acid sequences of different isolectins from the sponge Axinella polypoides (Schmidt)

The sponge Axinella polypoides contains four different D-galactose binding lectins and one, termed lectin IV, which is specific for hexuronic acids. Only the D-galactose binding lectins were investigated in this study. The complete amino-acid sequence of lectin I, the main component in the crude extract was determined. Lectin I is a homodimer and each subunit comprises 144 amino acids with a M(r) of 15,847 +/- 10, as calculated from the sequence data and determined by mass spectrometry. Each subunit contains one intrachain disulfide bridge between positions 4 and 46. Of lectin II, only the first 49 amino acids of the NH2-terminal end were analysed. This part has 29 amino acids in common with lectin I, including a cysteine residue at position 4, also suggesting an intrachain loop in a identical position as in lectin I. The molecular mass of its subunit is 16,235 +/- 10 Da. Only the first 15 NH2-terminal amino acids of lectins III and V could be sequenced. Lectin V was identical to lectin II in all positions, whereas lectin III showed only 5 residues identical to lectins I or II. Thus, lectins I, II and III are derived from three different genes, whereas lectin V may either be a proteolytic cleavage product, or result from different splicing events or may be derived also from a separate gene. Neither of the four lectins showed any similarity to known lectin sequences of animal or plant origin.

The amino-acid sequence of a lectin from conger eel, Conger myriaster, skin mucus

The amino-acid sequence of a beta-galactoside-binding lectin isolated from the skin mucus of the conger eel Conger myriaster was determined. The lectin (30 kDa) was composed of two identical subunits of 135 amino acid residues with N-acetylserine at the N-terminus and no half-cystinyl residue. It was a 30-34% sequence identical to vertebrate beta-galactoside-binding lectin and proved to be a member of the S-type lectin family.

Recovery of tryptophan in peptides and proteins by high-temperature and short-term acid hydrolysis in the presence of phenol

The addition of 3% (w/v) phenol to 6 M HCl largely prevented the destruction of tryptophan during rapid hydrolysis of peptides and proteins at 166 degrees C for 25 min or at 145 degrees C for 4 h. This hydrolysis procedure was advantageous for amino acid microanalysis using conventional high-performance liquid chromatography with a precolumn derivatization technique. The recovery of tryptophan from proteins was at least 80%. The addition of phenol also improved the recovery of methionine and carboxymethylcysteine. The amount of tryptophan in proteins electroblotted onto a polyvinylidene difluoride membrane was determined by this method.

The amino-acid sequence of multiple lectins of the acorn barnacle Megabalanus rosa and its homology with animal lectins

The amino-acid sequence of a lectin isolated from the coelomic fluid of the acorn barnacle Megabalanus rosa has been determined. The lectin (Mr 140,000) is a multimeric protein whose subunit consists of 173 amino acids and one carbohydrate chain attached to Asn-39. The amino-acid sequence was determined by the manual sequencing of peptides derived from the protein by digestion with Staphylococcus aureus V8 proteinase, lysine endopeptidase and chymotrypsin, as well as fragments produced by cleavage with cyanogen bromide. The amino-acid sequence of the lectin was compared with the sequence of one (Mr 64,000) of the multiple lectins of M. rosa. They are distinct molecules in spite of a significant homology in their amino-acid sequences. The amino-acid sequence includes some regions homologous to those in other invertebrate lectins, such as sea urchin and flesh fly lectins, and vertebrate lectins. This is the first report to show the amino-acid sequence of multiple lectins isolated from an invertebrate.

The positions of the disulfide bonds and the glycosylation site in a lectin of the acorn barnacle Megabalanus rosa

The positions of the interchain and intrachain disulfide bonds and the glycosylation site in a lectin of the acorn barnacle Megabalanus rosa were determined. The lectin (Mr 140,000) is composed of the same subunit (Mr 22,000) which is cross-linked by disulfide bonds to form a dimer. Intact lectin yielded two fragments, CB1 and CB2, by cleavage with cyanogen bromide. One intrachain and two interchain disulfide bonds were identified as Cys-53-Cys-61, Cys-14-Cys-50' and Cys-50-Cys-14', respectively, by enzymatic digestion and Edman degradation of CB1. Two intrachain disulfide bonds were determined as Cys-78-Cys-168 and Cys-144-Cys-160 by enzymatic digestion of CB2. The two intrachain disulfide bonds are well conserved through all invertebrate lectins and calcium-dependent animal lectins. S-Carboxamidomethylated lectin was digested with Staphylococcus aureus V8 proteinase and separated by reversed-phase HPLC. Glycopeptides were detected by the 4-N,N-dimethylamino-4'-azobenzene sulfonyl hyrazide method. Sequence analyses of the glycopeptides showed that a carbohydrate chain attached to Asn-39.

Homology of cytotoxic protein of eosinophilic leukocytes with IgE receptor Fc epsilon RII: implications for its structure and function

The major protein constituent of eosinophilic leukocyte granules is a cytotoxic protein that plays a key role in antiparasitic defence mechanisms and immune hypersensitivity reactions. We show here that the protein is homologous with animal lectins; it exhibits greatest similarity to the lectin domain of the low-affinity IgE receptor of lymphocytes. On the basis of homology with lectins the disulphide bond pattern of the protein is predicted. It is proposed that certain cysteines unique to major basic protein are on the surface of the molecule and are involved in forming disulphide-bonded polymers. Homology with IgE receptor raises the possibility that major basic protein may also bind to IgE antibodies. Such an interaction could provide an efficient way of targeting the cytotoxic protein to parasites and allergens recognized by IgE antibodies.

Cloning of a lymphocyte homing receptor reveals a lectin domain

Lymphocytes express cell surface molecules, termed homing receptors, that mediate their selective attachment to specialized high endothelial venules found within secondary lymphoid organs. Previous work has demonstrated that the adhesive interaction between lymphocytes and the endothelium of peripheral lymph nodes appears to involve a lectin-like activity. Moreover, MEL-14, a monoclonal antibody that blocks lymphocyte-peripheral lymph node binding and presumably recognizes the homing receptor mediating this adhesive interaction, appeared to detect the lectin-like receptor. In this paper we describe the cloning of a murine cDNA that encodes the antigen recognized by the MEL-14 antibody. Characterization of the cDNA encoding the putative mouse peripheral lymph node-specific homing receptor shows that it contains a lectin domain that appears to be involved in the binding of lymphocytes to peripheral lymph node endothelium, thus defining a new type of cellular adhesion molecule. This result supports a novel mechanism for the distribution of lymphocyte populations to various lymphoid organs.

Cloning of GMP-140, a granule membrane protein of platelets and endothelium: sequence similarity to proteins involved in cell adhesion and inflammation

GMP-140 is an integral membrane glycoprotein found in secretory granules of platelets and endothelial cells. After cellular activation, it is rapidly redistributed to the plasma membrane. The cDNA-derived primary structure of GMP-140 predicts a cysteine-rich protein with multiple domains, including a "lectin" region, an "EGF" domain, nine tandem consensus repeats related to those in complement-binding proteins, a transmembrane domain, and a short cytoplasmic tail. Some cDNAs also predict a soluble protein with a deleted transmembrane segment. The domain organization of GMP-140 is similar to that of ELAM-1, a cytokine-inducible endothelial cell receptor that binds neutrophils. This similarity suggests that GMP-140 belongs to a new family of inducible receptors with related structure and function on vascular cells.

Detecting distant homologies of mosaic proteins. Analysis of the sequences of thrombomodulin, thrombospondin complement components C9, C8 alpha and C8 beta, vitronectin and plasma cell membrane glycoprotein PC-1

Recognition of homologies may give hints about the structure and function of proteins; therefore, we are developing strategies to aid sequence comparisons. Detecting homology of mosaic proteins is especially difficult since the modules constituting these proteins are usually distantly related and their homology is not readily recognized by conventional computer programs. In the present work we show that the rules of the evolution of mosaic proteins can guide the identification of modules of mosaic proteins and can delineate the group of sequences in which the presence of homologous sequences may be expected. By this approach we can concentrate the search for homology to a limited group of sequences; thus ensuring a more intense and more fruitful search. The power of this approach is illustrated by the fact that it could detect homologies not identified by earlier methods of sequence comparison. In this paper we show that thrombomodulin contains a domain homologous with animal lectins, that complement components C9, C8 alpha and C8 beta have modules homologous with one of the repeat units of thrombospondin and that the somatomedin B module of vitronectin is homologous with the internal repeats of plasma cell membrane glycoprotein PC-1.

The amino-terminal domain of thrombomodulin and pancreatic stone protein are homologous with lectins

Amino acid sequence alignment of the amino-terminal of thrombomodulin and pancreatic stone protein with the hepatic asialoglycoprotein receptor shows that these proteins are homologous. From the known disulfide bridge pattern of other proteins belonging to the same family two disulfide bonds can be predicted. The homology raises the question whether the amino-terminal part of thrombomodulin and the pancreatic protein binds carbohydrate or perhaps like tetranectin have a specific affinity for other proteins.