Biomedical subjects

J P Carver

Publications and source records attributed to J P Carver.

At least 19 recordsLinked to original sources

PubMed1998

Studies on the conformational behaviour of GlcNAc-Man3-GlcNAc2 oligosaccharides using molecular dynamics simulations.

Three-dimensional structures of the natural substrate unit for the enzyme N-acetylglucosamine-transferase II, GIcNAc-Man3-GlcNAc2, were investigated by molecular modelling methods. Molecular dynamics (MD) and molecular mechanics calculations on two hexasaccharides, namely GlcNAc-Man3-GlcNAc2-Asn and GlcNAc-Man3-GlcNAc2-OMe were performed by the Biosym/MSI software using the CVFF and CFF95 force fields in vacuum. The MD simulations were calculated for 3 ns at different simulation temperatures and for two values of dielectric constant, epsilon=1 and epsilon=4. From each 3 ns trajectory, 3050 structures have been optimized. The local minima obtained have been clustered into families exhibiting similar values of glycosidic torsional angles phi, psi, and omega. The influence of the simulation conditions and force fields used on the conformational behaviour and structure of the title oligosaccharides is discussed.

Acetylglucosamine↗

PubMed1995

Solution structure of a cellulose-binding domain from Cellulomonas fimi by nuclear magnetic resonance spectroscopy.

Multidimensional, multinuclear nuclear magnetic resonance spectroscopy combined with dynamical simulated annealing has been used to determine the structure of a 110 amino acid cellulose-binding domain (CBD) from Cex, a beta-1,4-glycanase from the bacterium Cellulomonas fimi (CBDcex). An experimental data set comprising 1795 interproton NOE-derived restraints, 50 phi, 34 chi 1, and 106 hydrogen bond restraints was used to calculate 20 final structures. The calculated structures have an average root-mean-square (rms) deviation about the mean structure of 0.41 A for backbone atoms and 0.67 A for all heavy atoms when fitted over the secondary structural elements. Chromatography, ultracentrifugation, and 15N NMR relaxation experiments demonstrate that CBDcex is a dimer in solution. While attempts to measure NOEs across the dimer interface were unsuccessful, a computational strategy was employed to generate dimer structures consistent with the derived data set. The results from the dimer calculations indicate that, while the monomer topologies produced in the context of the dimer can be variable, the relative positioning of secondary structural elements and side chains present in the monomer are restored upon dimer formation. CBDcex forms an extensive beta-sheet structure with a beta-barrel fold. Titration with cellohexaose, [beta-D-glucopyranosyl-(1,4)]5-D-glucose, establishes that Trp 54 and 72 participate in cellulose binding. Analysis of the structure shows that these residues are adjacent in space and exposed to solvent. Together with other proximate hydrophilic residues, these residues form a carbohydrate-binding cleft, which appears to be a feature common to all CBDs of the same family.

Actinomycetales↗

PubMed1995

Inhibitors of carbohydrate processing: A new class of anticancer agents.

There is a need for anticancer agents with novel mechanisms of action. Recently identified molecular targets for new anticancer agents include inducers of cell differentiation, cell cycle arrest, and apoptosis, as well as signaling pathways for growth factors and cytokines. Another unexplored opportunity is presented by the ubiquitous intracellular glycoprotein glycosylation pathway. This complex process, concerned with the addition of sugars onto newly synthesized proteins, occurs in the lumen of the rough endoplasmic reticulum and in the Golgi. There are estimates of over 200 glycosyltransferase enzymes in this pathway, which results in considerable structural diversity of carbohydrates found on secreted and transmembrane glycoproteins. The specificity of glycosyltransferases for acceptors and sugar-nucleotide donors dictates linkage positions between sugars, anomeric configuration of linkages, and monosaccharide composition. Specific carbohydrate structures participate in cell-cell and cell-substratum interactions affecting processes such as lymphocyte trafficking, immune cell stimulation, embryogenesis, and cancer metastasis. Of the carbohydrate-processing inhibitors presently available, the alkaloid swainsonine, a Golgi alpha-mannosidase II inhibitor, is the first to have been selected for clinical testing based on its anticancer activity, p.o. availability, and low toxicity in mice. Herein, we review the rationale for targeting Golgi carbohydrate processing pathways in the treatment of cancer, and summarize the preclinical and clinical results with swainsonine. Prospects for the development of second generation inhibitors with improved specificity for Golgi-processing enzymes are discussed. Potential clinical applications of this new class of anticancer agents are emphasized.

Animals↗

PubMed1994

Synthesis of di- and tri-saccharides with intramolecular NH-glycosidic linkages: molecules with flexible and rigid glycosidic bonds for conformational studies.

Attempted dephthalimidation of the trisaccharide 1-O-acetyl-3,4-di-O-benzyl- 2,6-di-O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-glucopyranosyl )-alpha-D-mannopyranose (1) and its derivatives 2 and 3, as well as the disaccharide 1-O-acetyl-3,4,6-tri-O-benzyl-2-O-(3,4,6-tri-O-acetyl- 2-deoxy-2-phthalimido-beta-D-glucopyranosyl)-alpha-D-mannopyranose (13), with hydrazine hydrate in ethanol at 80 degrees C, produced the trisaccharide-6-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D- glucopyranosyl)-3,4-di-O-benzyl-beta-D-mannopyranose-3',4',6'-tri-O-a cet yl- beta-D-glucopyranose 1,2'-N:1',2-O-dianhydride (4) and 3,4,6-tri-O-benzyl-beta-D-mannopyranose 3',4',6'-tri-O-acetyl-beta-D-glucopyranose 1,2'-N:1',2-O-dianhydride (14), respectively, containing an intramolecular NH-glycosidic linkage. The conventional deblocking of compounds 4 and 14 gave the completely deblocked trisaccharide 6-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-beta-D-mannopyranose beta-D-glucopyranose 1,2'-N:1',2-O-dianhydride (6) and the disaccharide beta-D-mannopyranose beta-D-glucopyranose 1,2'-N:1',2-O-dianhydride (16), respectively, containing an intact intramolecular NH-glycosidic bond. The unusual intra NH-glycosyl character makes the linkage rigid, and therefore these compounds should not only be useful for NMR studies but also as substrates or inhibitors of GlcNAc-transferases.

Amides↗

PubMed1993

X-ray crystal structure of a pea lectin-trimannoside complex at 2.6 A resolution.

The x-ray crystal structure of pea lectin, in complex with a methyl glycoside of the N-linked-type oligosaccharide trimannosyl core, methyl 3,6-di-O-(alpha-D-mannopyranosyl)-alpha-D-mannopyranoside, has been solved by molecular replacement and refined at 2.6-A resolution. The R factor is 0.183 for all data in the 8.0 to 2.6 A resolution range with an average atomic temperature factor of 26.1 A2. Strong electron density for a single mannose residue is found in the monosaccharide-binding site suggesting that the trisaccharide binds primarily through one of the terminal alpha-linked mannose residues. The complex is stabilized by hydrogen bonds involving the protein residues Asp-81, Gly-99, Asn-125, Ala-217, and Glu-218, and the carbohydrate oxygen atoms O3, O4, O5, and O6. In addition, the carbohydrate makes van der Waals contacts with the protein, involving Phe-123 in particular. These interactions are very similar to those found in the monosaccharide complexes with concanavalin A and isolectin 1 of Lathyrus ochrus, confirming the structural relatedness of this family of proteins. Comparison of the pea lectin complex with the unliganded pea lectin and concanavalin A structures indicates differences in the conformation and water structure of the unliganded binding sites of these two proteins. Furthermore, a correlation between the position of the carbohydrate oxygen atoms in the complex and the bound water molecules in the unliganded binding sites is found. Binding of the trimannose core through a single terminal monosaccharide residue strongly argues that an additional fucose-binding site is responsible for the high affinity pea lectin-oligosaccharide interactions.

Amino Acid Sequence↗

PubMed1993

Flexibility in a tetrasaccharide fragment from the high mannose type of N-linked oligosaccharides.

An analysis has been carried out of the three-dimensional structure of a tetrasaccharide, Man(alpha 1-3)Man(alpha 1-6)Man(beta 1-4)GlcN Ac beta 1-OCD3, which is a fragment from the high mannose type of N-linked oligosaccharides. Although earlier work had suggested that this fragment might adopt a stable three-dimensional structure, both n.m.r. and conformational energy calculations support the existence of an ensemble of structures. The conformational entropy calculated from the ensemble and the distribution of distances between the terminal Man(alpha 1-3) and GlcN Ac residues, however, suggests that a significant fraction of the ensemble has the two terminal residues in close proximity.

Carbohydrate Conformation↗

PubMed1992

Detection of internal motions in oligosaccharides by 1H relaxation measurements at different magnetic fields.

The effect of internal motions on proton relaxation data in oligosaccharides has been investigated experimentally. 1H steady-state and transient NOEs together with 13C T1's have been measured at two magnetic field strengths. The existence of internal motions leads to additional modulations of the dipolar interaction between proton pairs, thus producing a range of spectral density functions for these interactions. As a result, it is possible to show that protons relaxing through fixed distances have a different ratio of relaxation parameters, acquired at 500 and 300 MHz, compared to those relaxing through fluctuating distances. This approach has been used to unequivocally establish for two disaccharides the existence of internal motions on the time scale of the overall tumbling.

Carbohydrate Conformation↗

PubMed1991

Molecular modelling of protein-carbohydrate interactions. Docking of monosaccharides in the binding site of concanavalin A.

A general procedure is described for addressing the computer simulation of protein-carbohydrate interactions. First, a molecular mechanical force field capable of performing conformational analysis of oligosaccharides has been derived by the addition of new parameters to the Tripos force field; it is also compatible with the simulation of protein. Second, a docking procedure which allows for a systematic exploration of the orientations and positions of a ligand into a protein cavity has been designed. This so-called 'crankshaft' method uses rotations and variations about/of virtual bonds connecting, via dummy atoms, the ligand to the protein binding site. Third, calculation of the relative stability of protein ligand complexes is performed. This strategy has been applied to search for all favourable interactions occurring between a lectin [concanavalin A (ConA)] and methyl alpha-D-mannopyranoside or methyl alpha-D-glucopyranoside. For each monosaccharide, different stable orientations and positions within the binding site can be distinguished. Among them, one corresponds to very favourable interactions, not only in terms of hydrogen bonding, but also in terms of van der Waals interactions. It corresponds precisely to the binding mode of methyl alpha-D-mannopyranoside into ConA as revealed by the 2.9 A resolution of the crystalline complex (Derewenda et al., 1989). Some implications of the present modelling study with respect to the molecular basis of the specificity of the interaction of lectins with various monosaccharides are presented.

Binding Sites↗

PubMed1989

Separation of the complex asparagine-linked oligosaccharides of the glycoprotein fetuin and elucidation of three triantennary structures having sialic acids linked only to galactose residues.

Asparagine-linked oligosaccharides of the glycoprotein fetuin were isolated as reducing oligosaccharides after hydrazinolysis/re-N-acetylation/mild acid treatment of the Pronase-digested glycoprotein. The sialylated oligosaccharides were separated by high-performance liquid chromatography in two different systems, which resulted in greater than 35 fractions, comprising di-, tri-, tetra-, and pentasialylated oligosaccharides. The major components were isomeric structures comprising the tri- and tetrasialylated fractions. In this and the accompanying paper (Cumming et al., 1989), the structures of 10 of the major components of the tri-, tetra-, and pentasialylated oligosaccharide fractions are described. Separation protocols and three isolated structures having sialic acid linked only to galactose are presented in this paper.

Asparagine↗

PubMed1989

Structures of asparagine-linked oligosaccharides of the glycoprotein fetuin having sialic acid linked to N-acetylglucosamine.

In the accompanying paper (Bendiak et al., 1989), the separation of a series of oligosaccharides released from asparagine residues of fetuin was described. A series of NMR experiments, which included one- and two-dimensional nuclear Overhauser enhancement, two-dimensional correlation spectroscopy, and two-dimensional relayed-coherence spectroscopy, as well as permethylation analyses, established a Gal beta 1----3(NeuAc alpha 2----6)GlcNAc beta 1----4Man unit common to a series of purified structures. These oligosaccharides contained either three, four, or five glycosidically linked sialic acid residues. The NeuAc residue in alpha 2----6 linkage to GlcNAc gives rise to diagnostic chemical shift perturbations of particular proton signals in the oligosaccharides.

Acetylglucosamine↗

PubMed1989

Control of glycoprotein synthesis. Detection and characterization of a novel branching enzyme from hen oviduct, UDP-N-acetylglucosamine:GlcNAc beta 1-6 (GlcNAc beta 1-2)Man alpha-R (GlcNAc to Man) beta-4-N-acetylglucosaminyltransferase VI.

Hen oviduct membranes were shown to contain high activity of a novel enzyme, UDP-GlcNac:GlcNAc beta 1-6(GlcNAc beta 1-2) Man alpha-R (GlcNAc to Man) beta 4-GlcNAc-transferase VI. The enzyme was shown to transfer GlcNAc in beta 1-4 linkage to the D-mannose residue of GlcNAc beta 1-6 (GlcNAc beta 1-2) Man alpha-R where R is either 1-6Man beta-(CH2)8COOCH3 or methyl. Radioactive enzyme products were purified by several chromatographic steps, including high performance liquid chromatography, and structures were determined by proton nmr, fast atom bombardment-mass spectrometry, and methylation analysis to be GlcNAc beta 1-6 ([14C]GlcNAc beta 1-4) (GlcNAc beta 1-2) Man alpha-R. The enzyme is stimulated by Triton X-100 and has optimum activity at a relatively high MnCl2 concentration of about 100 mM; Co2+, Mg2+, and Ca2+ could partially substitute for Mn2+. A tissue survey demonstrated high GlcNAc-transferase VI activity in hen oviduct and lower activity in chicken liver and colon, duck colon, and turkey intestine. No activity was found in mammalian tissues. Hen oviduct membranes cannot act on GlcNAc beta 1-6Man alpha-R but have a beta 4-GlcNAc-transferase activity that converts GlcNAc beta 1-2Man alpha-R to GlcNAc beta 1-4(GlcNAc beta 1-2) Man alpha-R where R is either 1-6Man beta-(CH2)8COOCH3 or 1-6Man beta methyl. The latter activity is probably due to GlcNAc-transferase IV which preferentially adds GlcNAc in beta 1-4 linkage to the Man alpha 1-3 arm of the GlcNAc beta 1-2Man alpha 1-6(GlcNAc beta 1-2Man alpha 1-3)Man beta 1-4GlcNAc beta 1-4GlcNAc-Asn core structure of asparagine-linked glycans. The minimum structural requirement for a substrate of beta 4-GlcNAc-transferase VI is therefore the trisaccharide GlcNAc beta 1-6(GlcNAc beta 1-2) Man alpha-; this trisaccharide is found on the Man alpha 6 arm of many branched complex asparagine-linked oligosaccharides. The data suggest that GlcNAc-transferase VI acts after the synthesis of the GlcNAc beta 1-2Man alpha 1-3-, GlcNAc beta 1-2Man alpha 1-6-, and GlcNAc beta 1-6 Man alpha 1-6-branches by GlcNAc-transferases I, II, and V, respectively, and is responsible for the synthesis of branched oligosaccharides containing the GlcNAc beta 1-6(GlcNAc beta 1-4)(GlcNAc beta 1-2)Man alpha 1-6Man beta moiety.

Acetylglucosamine↗

PubMed1989

Oligosaccharide-protein interactions: a three-dimensional view.

For carbohydrates to serve as recognition elements in cellular function, there must be 'receptors' which are capable of distinguishing between the multitude of oligosaccharide structures generated by a cell. Generally these receptors are assumed to be proteins, and the plant lectins have been used as model systems to examine the molecular basis for specificity in such interactions. Three aspects of the specificity of oligosaccharide-protein interactions will be discussed: (1) the conformational flexibility of oligosaccharides will be demonstrated through a quantitative analysis of nuclear magnetic resonance measurements; (2) a comparison of the measured and calculated values for the entropy barrier to oligosaccharide binding will be used to argue that the barrier arises from a loss of this conformational flexibility upon binding to the lectin (this conclusion is also supported by X-ray crystallographic studies); and (3) the thermodynamic model can be extended to the binding of glycoproteins to receptors and the high affinity of these interactions explained by either multivalency or fixation of the oligosaccharide in the 'correct' three-dimensional structure through interaction with the protein moiety.

Animals↗

PubMed1989

Separation of branched sialylated oligosaccharides using high-pH anion-exchange chromatography with pulsed amperometric detection.

Ten characterized sialylated oligosaccharides from bovine fetuin (B. Bendiak, M. Harris-Brandts, S. W. Michnick, J. P. Carver, and D. A. Cumming, Biochemistry, in press; and D. A. Cumming, C. G. Hellerqvist, M. Harris-Brandts, S. W. Michnick, J. P. Carver, and B. Bendiak, Biochemistry, in press) were chromatographed using high-performance anion-exchange chromatography with pulsed amperometric detection. At near neutral pH values, oligosaccharides were separated according to their number of formal negative charges from sialic acid; however, at alkaline pH, the neutral portion of the oligosaccharides enhanced resolution due to oxyanion formation. Specifically, trisialylated triantennary oligosaccharides containing a Gal-beta(1,3)GlcNAc sequence were more retained and could be completely separated from those having only Gal-beta(1,4)GlcNAc units. Oligosaccharides containing the same number of sialic acids were separated according to the combination of alpha(2,6)- and alpha(2,3)-linked sialic acids (alpha(2,6)-linked sialic acid reduced retention time). The relative molar electrochemical responses for di-, tri-, tetra-, and pentasialylated oligosaccharides were found to be similar (4.8 +/- 14% relative to glucose). Coelution studies were performed with each of the characterized oligosaccharides and the mixture of oligosaccharides which were released from fetuin with N-glycanase. The relative proportion of the major classes of sialylated oligosaccharides (bi-, tri-, tetra-, and penta-) varied significantly in bovine fetuin from different sources.

Chromatography, Ion Exchange↗

PubMed1988

Control of glycoprotein synthesis. The use of oligosaccharide substrates and HPLC to study the sequential pathway for N-acetylglucosaminyltransferases I, II, III, IV, V, and VI in the biosynthesis of highly branched N-glycans by hen oviduct membranes.

Glycoproteins isolated from hen oviduct contain highly branched asparagine-linked oligosaccharides (N-glycans). Six N-acetylglucosaminyltransferases (GlcNAc-T I, II, III, IV, V, and VI) are involved in initiating the synthesis of these branches, as indicated below: (formula; see text) where R is GlcNAc beta 1----4(+/-Fuc alpha 1----6)GlcNAcAsn-X. HPLC has been used to study the substrate specificities of these GlcNAc-T and the sequential pathways involved in the biosynthesis of highly branched N-glycans in hen oviduct. Oligosaccharides with free reducing GlcNAc termini were prepared from various glycoproteins by hydrazinolysis-re-N-acetylation and used as GlcNAc-T substrates and HPLC standards. Enzyme assay components were separated on AG1 x 8, followed by HPLC on amine-bonded silica columns eluted with acetonitrile-water mixtures. Absorbance at 195 nm and radioactivity of eluted compounds were monitored. Substrates and products were identified by comparison of their retention times with those of oligosaccharides with known structures. Enzyme assay by HPLC is more rapid and convenient than previous GlcNAc-T assays using lectin columns or electrophoresis. Since some substrates yielded multiple products, these could be used to assay more than one GlcNAc-T in the same incubation. GlcNAc-T VI was shown to act on both bisected and nonbisected GlcNAc-terminating tetraantennary oligosaccharide substrates; GlcNAc-T II, IV, and V acted poorly or not at all on bisected substrates. GlcNAc-T V was the only enzyme among the six transferases studied that could be assayed in the absence of Mn2+.

Animals↗

PubMed1987

Solution conformation of the branch points of N-linked glycans: synthetic model compounds for tri'-antennary and tetraantennary glycans.

The solution conformation of model compounds for the tri'-antennary and tetraantennary (six-arm) branch point of N-linked glycans has been determined through the use of chemical shift, relaxation, and nuclear Overhauser enhancement data. The object was to establish the conformation about the glycosidic linkages in the N-linked substructure GlcNAc(beta 1,6) [GlcNAc(beta 1,2)] Man(alpha)- by estimation of values for the appropriate glycosidic torsional angles. The GlcNAc(beta 1,6) linkage in a trisaccharide model compound was found to be constrained to a narrow rotameric subpopulation about the substituted Man C5-C6 bond (omega = -60 degrees) and a narrow range of possible phi - psi values. Free rotation about the Man C5-C6 bond was obstructed by unfavorable steric interactions between the GlcNAc(beta 1,6) and GlcNAc(beta 1,2) residues. A phi, psi value of 55 degrees, 190 degrees was found to be consistent with the NMR data for the GlcNAc(beta 1,6) linkage. However, the value of psi appears to be "virtual" in that the molecule is in equilibrium between two different values (90 degrees and 252 degrees). For the GlcNAc(beta 1,2) linkage, complete agreement between all the observed NMR parameters and all the calculated ensemble average values could only be obtained with a set of potential energy functions which included hydrogen bonding. Other choices of potentials yielded calculated values that disagreed with at least two of the observed quantities. As a result, we infer that an interresidue hydrogen bond is formed, and we find it to be between the GlcNAc(beta 1,2) ring oxygen and the Man C3 hydroxyl.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrate Conformation↗

PubMed1987

Virtual and solution conformations of oligosaccharides.

The possibility that observed nuclear Overhauser enhancements and bulk longitudinal relaxation times, parameters measured by 1H NMR and often employed in determining the preferred solution conformation of biologically important molecules, are the result of averaging over many conformational states is quantitatively evaluated. Of particular interest was to ascertain whether certain 1H NMR determined conformations are "virtual" in nature; i.e., the fraction of the population of molecules actually found at any time within the subset of conformational space defined as the "solution conformation" is vanishingly small. A statistical mechanics approach was utilized to calculate an ensemble average relaxation matrix from which (NOE)'s and (T1)'s are calculated. Model glycosidic linkages in four oligosaccharides were studied. The solution conformation at any glycosidic linkage is properly represented by a normalized, Boltzmann distribution of conformers generated from an appropriate potential energy surface. The nature of the resultant population distributions is such that 50% of the molecular population is found within 1% of available microstates, while 99% of the molecular population occupies about 10% of the ensemble microstates, a number roughly equal to that sterically allowed. From this analysis we conclude that in many cases quantitative interpretation of NMR relaxation data, which attempts to define a single set of allowable torsion angle values consistent with the observed data, will lead to solution conformations that are either virtual or reflect torsion angle values possessed by a minority of the molecular population. On the other hand, calculation of ensemble average NMR relaxation data yields values in agreement with experimental results. Observed values of NMR relaxation data are the result of the complex interdependence of the population distribution and NOE (or T1) surfaces in conformational space. In conformational analyses, NMR data can therefore be used to test different population distributions calculated from empirical potential energy functions.

Algorithms↗

PubMed1987

Reevaluation of rotamer populations for 1,6 linkages: reconciliation with potential energy calculations.

Applications of ensemble averaging to the solution conformation of model compounds for N-linked glycans are further investigated. Specifically, the interpretation usually applied to observed values of J5,6', a parameter reflecting the rotameric distribution about C5-C6 bonds (torsion angle omega in 1,6 glycosidic linkages) in 6-O-substituted hexopyranosides, was found to be inconsistent with populations derived from potential energy calculations. However, agreement between observed and calculated, ensemble-averaged values of J5,6' was obtained and the distribution of omega rotamers reinterpreted. Values of J5,6' that were previously interpreted as indicative of equipartition between two rotamers in fact reflect a marked preference for one of them. Additional potential energy terms, previously absent from energy calculations, are introduced and shown to be without effect on interpretations of omega rotamer distributions. From comparisons with both NMR relaxation and scalar coupling constant data, it is concluded that a simple empirical algorithm, HSEA, calculating van der Waals, exo-anomeric, and (as appropriate) hydrogen-bonding terms, is best suited for describing the population distributions in solution for oligosaccharides and N-linked glycans.

Carbohydrate Conformation↗

PubMed1987

Amino acid sequence differences in the alpha chains of pea seed isolectins: C-terminal processing.

The complete amino acid sequence of the alpha chains of both isolectins found in pea seeds has been determined using automated Edman degradation. We show that the alpha chains of these two proteins differ only at their C-termini: isolectin B is two amino acids longer than isolectin A. Furthermore, the alpha chains of both isolectins are shorter than would be predicted from the nucleotide sequence of a cDNA clone for pea lectin. We suggest, therefore, that these proteins arise from differential C-terminal processing. Amino acid composition data and C-terminal analysis show that the beta chains have also been processed at their C-termini, but in this case identical chains for both isolectins are produced.

Amino Acid Sequence↗