 |
PDBsum entry 1tlg
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
* Residue conservation analysis
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
The structure of a tunicate c-Type lectin from polyandrocarpa misakiensis complexed with d -Galactose.
|
|
|
Authors
|
|
S.F.Poget,
G.B.Legge,
M.R.Proctor,
P.J.Butler,
M.Bycroft,
R.L.Williams.
|
|
|
Ref.
|
|
J Mol Biol, 1999,
290,
867-879.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
C-type lectins are calcium-dependent carbohydrate-recognising proteins.
Isothermal titration calorimetry of the C-type Polyandrocarpa lectin (TC14) from
the tunicate Polyandrocarpa misakiensis revealed the presence of a single
calcium atom per monomer with a dissociation constant of 2.6 microM, and
confirmed the specificity of TC14 for D -galactose and related monosaccharides.
We have determined the 2.2 A X-ray crystal structure of Polyandrocarpa lectin
complexed with D -galactose. Analytical ultracentrifugation revealed that TC14
behaves as a dimer in solution. This is reflected by the presence of two
molecules in the asymmetric unit with the dimeric interface formed by
antiparallel pairing of the two N-terminal beta-strands and hydrophobic
interactions. TC14 adopts a typical C-type lectin fold with differences in
structure from other C-type lectins mainly in the diverse loop regions and in
the second alpha-helix, which is involved in the formation of the dimeric
interface. The D -galactose is bound through coordination of the 3 and
4-hydroxyl oxygen atoms with a bound calcium atom. Additional hydrogen bonds are
formed directly between serine, aspartate and glutamate side-chains of the
protein and the sugar 3 and 4-hydroxyl groups. Comparison of the galactose
binding by TC14 with the mannose binding by rat mannose-binding protein reveals
how monosaccharide specificity is achieved in this lectin. A tryptophan
side-chain close to the binding site and the distribution of hydrogen-bond
acceptors and donors around the 3 and 4-hydroxyl groups of the sugar are
essential determinants of specificity. These elements are, however, arranged in
a very different way than in an engineered galactose-specific mutant of MBPA.
Possible biological functions can more easily be understood from the fact that
TC14 is a dimer under physiological conditions.
|
|
|
|
|
|
|
|
Figure 5.
Figure 5. Ribbon diagram of the TC14 dimer. All elements of
secondary structure are labelled in the upper molecule, and
labelling is repeated for some elements in the lower molecule to
improve clarity. The sugar-binding calcium ions are shown as
grey spheres and the galactose molecules in a ball-and-stick
representation.
|
|
Figure 6.
Figure 6. Representation of the hydrophobic interactions at
the dimeric interface. The phenylalanine residues involved in
hydrophobic contacts are shown in ball-and-stick
representations. Molecule A is shown in light grey and molecule
B in dark grey.
|
|
|
|
|
|
The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(1999,
290,
867-879)
copyright 1999.
|
|
|
Secondary reference #1
|
|
|
Title
|
|
Expression of genes for 2 c-Type lectins during budding of the ascidian polyandrocarpa-Misakiensis
|
|
|
Authors
|
|
M.Shimada,
S.Fujiwara,
K.Kawamura.
|
|
|
Ref.
|
|
roux's arch dev biol, 1995,
204,
406.
|
|
|
|
Secondary reference #2
|
|
|
Title
|
|
Budding-Specific lectin induced in epithelial cells is an extracellular matrix component for stem cell aggregation in tunicates.
|
|
|
Authors
|
|
K.Kawamura,
S.Fujiwara,
Y.M.Sugino.
|
|
|
Ref.
|
|
Development, 1991,
113,
995.
|
|
|
PubMed id
|
|
|
|
|
|
|
|
|
Secondary reference #3
|
|
|
Title
|
|
A calcium-Dependent galactose-Binding lectin from the tunicate polyandrocarpa misakiensis. Isolation, Characterization, And amino acid sequence.
|
|
|
Authors
|
|
T.Suzuki,
T.Takagi,
T.Furukohri,
K.Kawamura,
M.Nakauchi.
|
|
|
Ref.
|
|
J Biol Chem, 1990,
265,
1274-1281.
|
|
|
PubMed id
|
|
|
|
|
|
|
|
|
|
|
|
|
