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INTRODUCTION |
Phytohemagglutinins from the Leguminosae family comprise one of
the largest group of homologous proteins with carbohydrate binding
properties (see Ref. 1). Despite similarities in their physicochemical
properties and their relatively conserved primary sequences,
Leguminosae lectins display considerable diversity in their
carbohydrate binding properties (2). This diversity is present not only
in terms of recognizing different monosaccharides but also in lectins
with the same nominal monosaccharide specificity. For example,
Man-specific Leguminosae lectins have been isolated from the Diocleinae
subtribe, which include the jack bean lectin concanavalin A
(ConA)1 and seed lectin from
Dioclea grandiflora, and from the Vicieae tribe, which
includes the sweet pea, garden pea, lentil, and fava bean lectins.
However, ConA and D. grandiflora lectin have recently been
shown to possess substantially enhanced affinities for the "core"
trimannoside,
3,6-di-O-(
-D-mannopyranosyl)-D-mannose, which is present in all asparagine-linked (N-linked)
carbohydrates (3, 4). In addition, recent hemagglutination inhibition studies have reported that ConA and D. grandiflora lectin
have nearly the same pattern of binding to deoxy analogs
2-11 of the trimannoside (Fig. 1) (4). These studies
indicate that two nominal Man/Glc-specific lectins from the Diocleinae
subtribe (Scheme I
), possess extended
binding sites and high affinities for the trimannoside, unlike members
of the Vicieae tribe (1). In addition, the hemagglutination
inhibition study showed that, while ConA possesses high affinity for a
biantennary complex carbohydrate (14, Fig.
1), D. grandiflora
lectin shows much lower affinity for the oligosaccharide (4). These
results indicate a further divergent specificity of these two
Diocleinae subtribe lectins for complex type carbohydrates.

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Fig. 1.
Structures of core trimannoside 1, deoxy analogs 2-12, Man5 oligomannose carbohydrate 13, and biantennary
complex carbohydrate 14. Man, GlcNAc,
2-dMan, 3-dMan, 4-dMan, and
6-dMan represent mannose, N-acetylglucosamine,
2-deoxymannose, 3-deoxymannose, 4-deoxymannose, and 6-deoxymannose
residues, respectively. 1, methyl
3,6-di-O-( -D-mannopyranosyl)- -D-mannopyranoside;
2, me- thyl
6-O-( -D-mannopyranosyl)-3-O-(2-deoxy- -D-mannopyranosyl)- -D-manno-pyranoside;
3, methyl
6-O-( -D-mannopyranosyl)-3-O-(3-deoxy- -D-mannopyranosyl)- -D-mannopyranoside;
4, methyl
6-O-( -D-mannopyranosyl)-3-O-(4-deoxy- -D-mannopyranosyl)- -D-mannopyranoside;
5, methyl
6-O-( -D-mannopyranosyl)-3-O-(6-deoxy- -D-mannopyranosyl)- -D-mannopyranoside;
6, methyl
6-O-(2-deoxy- -D-mannopyranosyl)-3-O-( -D-mannopyranosyl)- -D-mannopyranoside;
7, methyl
6-O-(3-deoxy- -D-mannopyranosyl)-3-O-( -D-mannopyranosyl)- -D-mannopyranoside;
8, me-thyl
6-O-(4-deoxy- -D-mannopyranosyl)-3-O-( -D-mannopyranosyl)- -D-mannopyranoside;
9, methyl
6-O-(6-deoxy- -D-mannopyranosyl)-3O-( -D-mannopyranosyl)- -D-mannopyranoside;
10, methyl
6-O( -D-mannopyranosyl)-3-O-( -D-mannopyranosyl)-2-deoxy- -D-mannopyranoside;
11, methyl
6-O-( -D-mannopyranosyl)-3-O-( -D-mannopyranosyl)-4-deoxy- -D-mannopyranoside;
12, methyl
6-O-( -D-mannopyranosyl)-3-O-(3,4-dideoxy- -D-mannopyranosyl)-2,4-dideoxy- -Dmannopyranoside.
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Isothermal titration microcalorimetry (ITC) has been used to determine
the thermodynamics of carbohydrate binding to ConA (3, 5, 6), including
binding of the methyl
-anomer of the core trimannoside
(1) and its deoxy analogs (2-11) (7). The
thermodynamic data (7) identified the 3-, 4- and 6-OH of the
(1-6)-Man, the 3- and 4-OH of the
(1-3)-Man, and the 2- and
4-hydroxyls of the central Man of 1 in binding, confirming
the hemagglutination results (4). Importantly, both the
hemagglutination inhibition (4) and ITC data (7) agree with the
recently determined x-ray crystal structure of ConA complexed with the
trimannoside (8), which shows binding of the above hydroxyls of the
trisaccharide (Fig. 2).

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Fig. 2.
View of the x-ray crystal structure of
trimannoside 1 (no anomeric methoxy group) bound to ConA. The
trimannoside is shown with the central Man indicated by C,
the (1-6)-Man by 6, and the (1-3)-Man by
3. Data are from Naismith and Field (8).
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Seven other lectins of the subtribe Diocleinae from different genera
and different species (Scheme I) have recently been described. The
lectins are from Canavalia brasiliensis, Canavalia
bonariensis, Cratylia floribunda, Dioclea
rostrata, Dioclea virgata, Dioclea violacea,
and Dioclea guianensis. The SDS-polyacrylamide gel
electrophoresis patterns of the subunit structures of the lectins
resemble ConA and D. grandiflora lectin, with molecular
masses ranging from 26 to 30 kDa (9-15). The x-ray crystal structure
of C. brasiliensis has recently been reported (16) and is
similar to ConA (17, 18). Although the complete primary sequences of
all of the Diocleinae lectins are not known, the high degree of
sequence homologies of ConA, D. grandiflora, and C. brasiliensis suggests that other members of the Diocleinae
subtribe possess relatively conserved sequences.
Despite their phylogenetic proximity and apparently conserved
sequences, the above Diocleinae lectins possess different biological activities such as histamine release from rat peritoneal mast cells
(19), lymphocyte proliferation and interferon-
production (20),
peritoneal macrophage stimulation and inflammatory reaction (21), and
induction of paw edema and peritoneal cell immigration in rats (22).
Thus, it is important to determine the fine carbohydrate binding
specificities of this group of lectins.
The present study reports hemagglutination inhibition and ITC studies
of the binding of the above seven new Diocleinae lectins to a variety
of mono- and oligosaccharides, trimannoside 1, deoxy analogs
2-12, Man5 oligomannose carbohydrate 13, and
biantennary complex carbohydrate 14 (Fig. 1). Together with
results for ConA and D. grandiflora lectin, the present
findings indicate that nine members of the Diocleinae subtribe of
Leguminosae lectins possess conserved binding specificities toward
1 but differential specificities for 14.
Furthermore, the relative affinities of the lectins for 14 correlate with their abilities to stimulate histamine release from the
rat peritoneal mast cells.
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MATERIALS AND METHODS |
Me
Glc, Me
Man, methyl-
-D-glucopyranoside,
2-deoxy-D-glucose, Gal, Fuc, Man
1-2Man, Man
1-3Man,
Man
1-6Man, maltose, trehalose, maltotriose, lactose, melibiose,
sialic acid, and 1 were purchased from Sigma.
Methyl-2-deoxy-
-D-mannopyranoside was a gift from Dr. S. Sabesan (DuPont). Biantennary complex carbohydrate 14,
GlcNAc
1-2Man, and Man5 oligosaccharide (13) were
obtained from Dextra Laboratories Ltd. The synthesis of
oligosaccharides 2-11 (Fig. 1) has been described elsewhere
(23). Synthesis of 12 will be presented elsewhere. The
concentrations of carbohydrates were measured by the phenol-sulfuric
acid method using an appropriate mixture of Man, Glc, and Gal as the
standard (24, 25). The purity of the oligosaccharides was checked by 500-MHz 1H NMR spectroscopy. Seeds of all of the species
were obtained from the States of Ceara and Rio Grande do Sul, Brazil.
Purification of the Lectins--
Lectins were purified by
affinity chromatography using Sephadex G-50, as described previously
(see Ref. 26). Concentrations of the lectins were determined
spectrophotometrically at 280 nm and expressed in terms of monomer. The
A1 cm1% at pH 7.2 and the
subunit molecular mass of the lectins used are as follows: 10.47 and 26 kDa (C. brasiliensis) (9), 11.15 and 30 kDa (C. bonariensis) (13), 11.36 and 29.5 kDa (C. floribunda) (10), 11.22 and 30 kDa (D. rostrata) (12), 10.50 and 30 kDa (D. guianensis) (11), 10.19 and 30 kDa (D. virgata) (14), 9.75 and 29.5 kDa (D. violacea) (15).
A1 cm1% of C. floribunda, D. rostrata, and D. violacea
were reported above, whereas that of the remaining lectins were
determined in the present study.
Hemagglutination Inhibition Assay--
The assay was performed
at room temperature using a 2-fold serial dilution technique (27) and
3% (v/v) rabbit erythrocytes in HEPES buffer (0.1 M HEPES,
0.15 M NaCl, 1 mM CaCl2, and 1 mM MnCl2, pH 7.2). The minimum concentration of
saccharide required for complete inhibition of four hemagglutination
doses was determined by visual inspection.
Isothermal Titration Microcalorimetry--
ITC experiments were
performed using an OMEGA Microcalorimeter from Microcal, Inc.
(Northampton, MA). In individual titrations, injections of 4 µl of
carbohydrate were added from the computer-controlled 250-µl
microsyringe at an interval of 4 min into the lectin solution (cell
volume = 1.3424 ml) dissolved in the same buffer as the saccharide, while stirring at 350 rpm. An example of an ITC experiment is shown in Fig. 3 for binding of
1 to D. violacea at 27 °C. Control experiments
performed by making identical injections of saccharide into a cell
containing buffer with no protein showed insignificant heats of
dilution. The experimental data were fitted to a theoretical titration
curve using software supplied by Microcal, with
H
(enthalpy change in kcal mol
1), Ka
(association constant in M
1), and
n (number of binding sites/monomer), as adjustable
parameters. The quantity c = Ka
Mt(0), where Mt(0) is the initial
macromolecule concentration, is of importance in titration
microcalorimetry (28). All experiments were performed with c
values 1 < c < 200. The instrument was
calibrated using the calibration kit containing ribonuclease A (RNase
A) and cytidine 2'-monophosphate supplied by the manufacturer.
Thermodynamic parameters were calculated from the equation,
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(Eq. 1)
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where
G,
H, and
S are
the changes in free energy, enthalpy, and entropy of binding.
T is the absolute temperature, and r = 1.98 cal mol
1 K
1.

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Fig. 3.
ITC profile of D. violacea (0.18 mM) with trisaccharide 1 (9.7 mM) at
27 °C. Top, data obtained for 30 automatic injections, 4 µl each, of 1; bottom, the integrated curve
showing experimental points ( ) and the best fit ( ). The buffer
was 0.1 M HEPES with 1.0 M NaCl and 5 mM each CaCl2 and MnCl2 (pH 7.2).
For details, see "Materials and Methods."
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RESULTS AND DISCUSSION |
Monosaccharide Binding Specificities--
The monosaccharide
binding properties of ConA (29) and D. grandiflora lectin
(4, 30) are well defined, with both lectins showing preferential
binding to the
-pyranosides of Man and Glc. The seven other
Diocleinae lectins in Table I generally
show similar preferential binding to the
-pyranosides of Man and
Glc, and not to Gal, Fuc, lactose, melibiose, or sialic acid. The C-2 hydroxyl group of Man is not essential for binding to the Diocleinae lectins, since methyl 2-deoxy-
-D-mannopyranoside is as
potent as Me
Man. Methyl 2-deoxy-
-D-mannopyranoside
was previously reported not to inhibit D. grandiflora lectin
(4); however, a reinvestigation shows that it does inhibit the lectin
(Table I). 2-D-Glc inhibits C. floribunda,
D. rostrata, and D. guianensis more poorly than Glc. GlcNAc at a relatively high concentration (150 mM)
shows some inhibition of C. brasiliensis, C. bonariensis, and D. virgata but did not inhibit the
other four lectins. 3-deoxymannose, 4-deoxymannose, and 6-deoxymannose
show no inhibitory activity, suggesting that Diocleinae lectins
recognize the 3-, 4-, and 6-hydroxyl groups of Man, as observed for
ConA (29) and D. grandiflora lectin (4).
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Table I
Inhibitory potencies of monosaccharides and disaccharides for
Diocleinae lectin-mediated hemagglutination of rabbit erythrocytes
Values in parenthesis are normalized with respect to Me Man for each
lectin.
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The thermodynamic binding parameters of the seven new Diocleinae
lectins to Me
Man determined by ITC measurements are listed in Table
III. The thermodynamic parameters for ConA (5) and D. grandiflora lectin (3) binding to Me
Man have previously been
reported and are listed in Table III for comparison. The values for
D. grandiflora lectin binding to Me
Man have been
reexamined and confirmed in the present study. C. brasiliensis displays the highest Ka value
(1.3 × 104 M
1), with
D. rostrata possessing the lowest Ka
value (1.7 × 103 M
1).
C. brasiliensis, D. guianensis, D. violacea, and D. virgata have
H values
between
5.8 and
4.9 kcal mol
1, while C. bonariensis, C. floribunda, D. rostrata,
ConA, and D. grandiflora possess 
H values
between
6.9 and
8.9 kcal mol
1. However, the relative
Ka values of the lectins for binding Me
Man do not
correlate with their respective 
H values, indicating
compensating entropic factors.
Disaccharide Binding Specificities--
Inhibitory potencies of
most of the disaccharides for the seven Diocleinae lectins were
comparable with that of ConA and D. grandiflora lectin
(Table I). None of the lectins were inhibited by lactose and melibiose,
as expected. It has previously been shown that the affinity of ConA for
Man
(1-2)Man, a disaccharide moiety found in N-linked
oligomannose carbohydrates, is 5-fold greater than Me
Man, as
compared with weaker binding of D. grandiflora lectin to the
disaccharide relative to the monosaccharide (4). The seven new
Diocleinae lectins display a range of relative affinities for
Man
(1-2)Man. D. virgata shows 16-fold greater affinity
for the disaccharide relative to Me
Man, whereas D. guianensis and D. violacea show enhanced affinities for
the disaccharide comparable with that of ConA. The remaining four
lectins show lower relative affinities for the disaccharide.
Large differences in the binding specificity of ConA and D. grandiflora lectin toward GlcNAc(
1-2)Man, a disaccharide
moiety found in a variety of N-linked carbohydrates, have
been reported (4). While ConA binds to the disaccharide, no binding was
detected for D. grandiflora lectin. This is consistent with
the difference in relative affinities of ConA and D. grandiflora lectin for biantennary complex carbohydrate
14 (Fig. 1) (Table II), with
ConA showing high affinity for the pentasaccharide but D. grandiflora lectin showing low affinity (4). The other Diocleinae
lectins exhibit distinct patterns of binding to GlcNAc(
1-2)Man.
While C. brasiliensis, D. guianensis, and
D. virgata bind the disaccharide, the remaining lectins show
little or no affinity for it, similar to D. grandiflora
lectin. This observation is significant in light of the results for
binding of the lectins to biantennary carbohydrate 14,
discussed below.
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Table II
Inhibitory potencies of trimannoside 1 and its deoxy
analogues for Diocleinae lectin-mediated hemagglutination of rabbit
erythrocytes
Inhibitory potencies in parentheses are relative to trimannoside
1 for each lectin.
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Binding to Trimannoside 1 and Its Deoxy
Analogs--
ConA is known to possess high affinity for the
trisaccharide,
3,6-di-O-(
-D-mannopyranosyl)-D-mannose,
which is present in the core region of all asparagine-linked
carbohydrates (31). ITC data established that ConA binds to the
trimannoside and its methyl
-anomer (1) with a nearly
6
kcal mol
1 greater 
H and a 60-fold greater
Ka than Me
Man (5). These results suggested
extended site binding of ConA to the trimannoside, which was confirmed
by the x-ray crystal structure of the trimannoside-ConA complex (Fig.
3) (8). ITC studies of ConA binding to deoxy analogs 2-11
established the binding energetics of the various hydroxyl groups of
trimannoside 1 to ConA (7). The results also demonstrated
that the solution complex of the trimannoside involves binding of the
same hydroxyl groups of 1 observed in the x-ray crystal
complex. Thus, ConA binds to 1 via the 3-, 4-, and
6-hydroxyls on the
(1-6)-Man residue, the 2- and 4-hydroxyls of the
central Man residue, and the 3- and 4-hydroxyls of the
(1-3)-Man
residue (Fig. 2).
Chervenak and Toone (3) reported similar enhanced 
H and
Ka values for D. grandiflora lectin
binding to 1 relative to Me
Man, which were confirmed in
the present study (Table III). In
addition, hemagglutination inhibition experiments with deoxy analogs
2-11 established that the pattern of binding of the
hydroxyl groups of 1 to D. grandiflora lectin is
similar to that for ConA (Table II for comparison) (4). These findings
suggest similar extended sites for both lectins to the
trimannoside.
Hemagglutination inhibition data in the present study (Table II) show
that the seven new Diocleinae lectins exhibit similar enhanced
affinities for 1 relative to Me
Man, as observed for ConA
and D. grandiflora lectin. ITC data shown in Table III indicate that all seven new Diocleinae lectins show enhanced
Ka and 
H values for 1 relative to Me
Man. The enhanced Ka values of the
lectins for 1 relative to Me
Man are shown in Fig.
4. The 
H values for all
seven lectins binding to 1 are
5 to
7 kcal
mol
1 greater than that for Me
Man, similar to the
differences observed for ConA and D. grandiflora lectin
(Table III). These data strongly suggest similar extended binding sites
for all nine Diocleinae lectins.

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Fig. 4.
Plot of the ratio of Ka
values of the nine Diocleinae lectins for trimannoside 1 and complex
carbohydrate 14, relative to Me Man, derived from the ITC data in
Table III.
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In order to determine which hydroxyl groups of 1 are
involved in binding to the Diocleinae lectins, hemagglutination inhibition experiments were performed using monodeoxy analogs 2-11 and tetradeoxy analog 12 (Table II). As an example, hemagglutination inhibition data for the C. floribunda lectin are shown in Fig.
5. The results indicate the involvements of the 3-, 4-, and 6-hydroxyls of the
(1-6)-Man, the 3- and
4-hydroxyls of the
(1-3)-Man, and the 2- and 4-hydroxyls of the
central Man of trimannoside 1 in binding. There is also an
indication of possible participation of the 2-hydroxyl of the
(1-6)-arm, as observed for a few of the lectins in Table II. As
expected, tetradeoxy analog 12 shows very little inhibition
potency relative to 1 and is comparable with that of
Me
Man. The data in Table II show a similar pattern of inhibition by
the analogs for the seven new Diocleinae lectins as observed for ConA
and D. grandiflora lectin (4). These results indicate highly
conserved binding sites for 1 in all nine Diocleinae
lectins.

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Fig. 5.
Plot of the hemagglutination inhibition
potencies of deoxy analogs 2-12 (Fig. 1) in the presence of C. floribunda lectin.
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Binding of Man5 Oligomannose Carbohydrate--
Hemagglutination
inhibition data in Table II show that the Diocleinae lectins bind Man5
oligosaccharide 13 with almost the same inhibitory potency
as 1. This indicates that the trimannoside moiety on the
(1-6)-arm is the primary epitope for interaction, as observed for
ConA and D. grandiflora lectin (4).
Binding of Biantennary Complex Oligosaccharide
14--
The affinities of D. grandiflora lectin
for biantennary complex oligosaccharide 14 and the longer
chain analog with terminal Gal residues have been reported to be weak
compared with that of ConA (4). These results are related to
the lack of D. grandiflora lectin binding to the
disaccharide GlcNAc
1-2Man, which is present in 14 (Table
I) (4). All of the Diocleinae lectins tested showed distinct correlated
binding affinities toward this disaccharide and 14.
Hemagglutination inhibition data in Table II indicates that
14 has much higher inhibition potencies with C. brasiliensis, D. guianensis, and D. virgata as compared with the other new lectins. Longer chain analogs of 14 also show a similar pattern (data not shown). This
parallels the binding activities of the lectins toward GlcNAc
1-2Man
(Table I). In addition, ITC data in Table III show an order of
magnitude greater Ka values of C. brasiliensis, D. guianensis, and D. virgata
for 14 relative to the other four lectins. Among the nine
Diocleinae lectins, ConA shows the highest Ka value
for 14, with D. grandiflora lectin showing a
relatively low Ka. The relative
Ka values for all nine lectins binding to
14 (along with 1) with respect to Me
Man are
shown in Fig. 4. Table III also shows that C. brasiliensis, D. guianensis, and D. virgata possess greater

H values for 14 of the seven new lectins,
and that ConA possesses the greatest 
H value of the
nine lectins.
Importantly, an enthalpy-entropy compensation plot (
H
versus
T
S) of the data in Table III for
14 shows different slopes for the above two groups of the
Diocleinae lectins (Fig. 6B).
The lectins from C. brasiliensis, D. guianensis,
D. virgata, and ConA fall on a line with a slope of 1.44 (correlation coefficient 0.85), while the lectins from C. bonariensis, C. floribunda, D. rostrata,
D. violacea, and D. grandiflora fall on a line
with a slope of 0.85 (correlation coefficient 0.98). Although the
D. grandiflora data point appears to intersect both plots,
it is associated with the latter group of lectins because of its
relatively low affinity and 
H values for 14.
By comparison, a similar plot of the lectins binding to 1 shows a single line with a slope of 1.21 (correlation coefficient 0.97)
(Fig. 6A). These results indicate different energetic
mechanisms of binding of the four relatively high affinity lectins to
14, as compared with the five lower affinity lectins. Thus,
although all nine Diocleinae lectins show conserved high affinities
binding for 1, four of the lectins show relatively high
affinities for 14, with the other five lectins showing
relatively low affinities. Therefore, binding discrimination among this
group of lectins occurs toward biantennary complex carbohydrates. The structural basis for this discrimination is currently under
investigation.

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Fig. 6.
Enthalpy-entropy compensation plots for the
binding of the Diocleinae lectins with trimannoside 1 (slope = 1.21) (A) and biantennary complex carbohydrate 14 at
27 °C (300 K) (B). In B, closed
circles ( ) represent the values for ConA, C. brasiliensis, D. guianensis, and D. virgata
(slope = 1.4) while the closed squares ( ) represent
the values for D. grandiflora, C. bonariensis,
C. floribunda, D. rostrata, and D. violacea (slope = 0.85).
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Histamine Release Activities of the Diocleinae Lectins Are
Correlated with Relative Affinities for 14--
ConA has
long been known for its ability to induce histamine release from cells
(see Refs. 32 and 33). Recently, Gomes and co-workers (19) investigated
the histamine release properties from rat peritoneal mast cells of
several other lectins from the same subtribe. At the level of 10 µg/ml lectin concentration, ConA, C. brasiliensis,
D. guianensis, and D. virgata induced a higher
level of histamine release from rat peritoneal mast cells, whereas
D. grandiflora, C. bonariensis, C. floribunda, D. rostrata, and D. violacea
displayed lower abilities for induction. A significant correlation
between the histamine releasing properties of these lectins and their
affinity constants for 14 is apparent from the present
study. Fig. 7 shows that the
Ka values of the Diocleinae lectins for
14 and the amount of histamine released by the lectins at 10 µg/ml are correlated. The strong histamine-inducing lectins ConA,
C. brasiliensis, D. guianensis, and D. virgata exhibit relatively high affinities
(Ka) for 14. On the other hand, the
remaining relatively inactive lectins possess lower affinities for the
complex carbohydrate. It appears, therefore, that induction of
histamine release from rat peritoneal mast cells by ConA, C. brasiliensis, D. guianensis, and D. virgata
involves binding of the lectins to a biantennary complex carbohydrate
and/or structurally homologous epitope present on the cell surface.

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Fig. 7.
Graph showing Ka values
(gray bars) of the nine Diocleinae lectins for complex
carbohydrate 14 and their histamine releasing properties (black
bars). The data of histamine release are taken from Gomes
et al. (19).
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Conclusions--
The present study demonstrates that nine lectins
from the Diocleinae subtribe are Man/Glc-binding proteins with
conserved binding specificities for the core trimannoside of
N-linked carbohydrates. Using deoxy analogs of the
trimannoside, all nine lectins were shown to possess conserved binding
sites that recognize the 3-, 4-, and 6-hydroxyl groups on the
(1-6)-Man, the 3- and 4-hydroxyl groups on the
(1-3)-Man, and
the 2- and 4-hydroxyl groups of the central Man of the trimannoside.
While the binding specificities of the lectins are conserved for the
trimannoside, their specificities are different for biantennary complex
carbohydrate 14 and longer chain analogs. Thermodynamic data
from ITC experiments indicate different energetic mechanisms of binding
of the Diocleinae lectins to 14. The relative affinities of
the lectins for 14 correlate with their induced histamine
release activities from rat peritoneal mast cells, suggesting that the
lectin receptors on the cells involve a carbohydrate(s) structure
similar to 14.