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PDBsum entry 1j4t
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Plant protein
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PDB id
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1j4t
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Crystal structures of artocarpin, A moraceae lectin with mannose specificity, And its complex with methyl-Alpha-D-Mannose: implications to the generation of carbohydrate specificity.
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Authors
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J.V.Pratap,
A.A.Jeyaprakash,
P.G.Rani,
K.Sekar,
A.Surolia,
M.Vijayan.
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Ref.
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J Mol Biol, 2002,
317,
237-247.
[DOI no: ]
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PubMed id
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Abstract
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The seeds of jack fruit (Artocarpus integrifolia) contain two tetrameric
lectins, jacalin and artocarpin. Jacalin was the first lectin found to exhibit
the beta-prism I fold, which is characteristic of the Moraceae plant lectin
family. Jacalin contains two polypeptide chains produced by a post-translational
proteolysis which has been shown to be crucial for generating its specificity
for galactose. Artocarpin is a single chain protein with considerable sequence
similarity with jacalin. It, however, exhibits many properties different from
those of jacalin. In particular, it is specific to mannose. The structures of
two crystal forms, form I and form II, of the native lectin have been determined
at 2.4 and 2.5 A resolution, respectively. The structure of the lectin complexed
with methyl-alpha-mannose, has also been determined at 2.9 A resolution. The
structure is similar to jacalin, although differences exist in details. The
crystal structures and detailed modelling studies indicate that the following
differences between the carbohydrate binding sites of artocarpin and jacalin are
responsible for the difference in the specificities of the two lectins. Firstly,
artocarpin does not contain, unlike jacalin, an N terminus generated by
post-translational proteolysis. Secondly, there is no aromatic residue in the
binding site of artocarpin whereas there are four in that of jacalin. A
comparison with similar lectins of known structures or sequences, suggests that,
in general, stacking interactions with aromatic residues are important for the
binding of galactose while such interactions are usually absent in the
carbohydrate binding sites of mannose-specific lectins with the beta-prism I
fold.
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Figure 1.
Figure 1. Structure of artocarpin. (a) Schematic
representation showing hydrogen bonds. (b) The subunit with the
three Greek keys coloured differently. (c) Quaternary structure
with the four subunits coloured differently. Figures 1(b) 4 were
prepared using BOBSCRIPT. [44]
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Figure 3.
Figure 3. (a) Stereo view of the sugar molecule in the A
subunit with the 2|F[o]| -|F[c]| map contoured at 1s and (b)
hydrogen bonds observed between the protein and sugar.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2002,
317,
237-247)
copyright 2002.
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