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PDBsum entry 1b44
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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 structure of the b subunit of escherichia coli heat-Labile enterotoxin carrying peptides with anti-Herpes simplex virus type 1 activity.
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Authors
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D.Matković-Calogović,
A.Loregian,
M.R.D'Acunto,
R.Battistutta,
A.Tossi,
G.Palù,
G.Zanotti.
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Ref.
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J Biol Chem, 1999,
274,
8764-8769.
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PubMed id
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Abstract
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Two chimeric proteins, consisting of the B subunit of Escherichia coli
heat-labile enterotoxin with different peptides fused to the COOH-terminal ends,
have been crystallized and their three-dimensional structure determined. The two
extensions correspond to (a) a nonapeptide representing the COOH-terminal
sequence of the small subunit of herpes simplex virus type 1 ribonucleotide
reductase and (b) a 27-amino acid long peptide, corresponding to the
COOH-terminal end of the catalytic subunit (POL) of DNA polymerase from the same
virus. Both proteins crystallize in the P41212 space group with one pentameric
molecule per asymmetric unit, corresponding to a solvent content of about 75%.
The overall conformation of the B subunit pentamer in the two chimeric proteins,
which consists of five identical polypeptide chains, is very similar to that in
the native AB complex and conforms strictly to 5-fold symmetry. On the contrary,
the peptide extensions are essentially disordered: in the case of the
nonapeptide, only 5 and 6 amino acids were, respectively, positioned in two
monomers, while in the other three only 2 residues are ordered. The extension is
fully confined to the surface of the pentamer opposite to the face that
interacts with the membrane and consequently it does not interfere with the
ability of the B subunit to interact with membrane receptors. Moreover, the
conformational flexibility of the two peptide extensions could be correlated to
their propensity for proteolytic processing and consequent release of a
biologically active molecule into cultured cells.
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Figure 2.
Fig. 2. Schematic drawing of the overall structure of the
EtxB-R2 pentamer, prepared with the MOLSCRIPT program (37). The
portion of peptide extensions visible in the electron density
map are in black. Arrows indicate the loop 54-61. The amino acid
sequences of COOH terminus of the two fusion proteins, from
residue 102, are (peptide extensions in bold letters): EtxB-R2,
... Glu-Lys-Leu-Tyr-Ala-Gly-Ala-Val-Val-Asn-Asp-Leu; EtxB-Pol,
...
Glu-Lys-Leu-Ala-Gly-Phe-Gly-Ala-Val-Gly-Ala-Gly-Ala-Thr-Ala-Glu-Glu-Thr-Arg-Arg-Met-Leu-His-Arg-Ala-Phe-Asp-Thr-Leu-Ala.
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Figure 4.
Fig. 4. Stereo drawing of the C  chain trace
of the EtxB-R2 subunit, with all the atoms superimposed for each
extension: amino acids from 103 to 108 in chain D, from 103 to
109 in chain F, from 103 to 105 in chains E, G, and H. The five
sulfate ions close to Lys^103 are also shown.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(1999,
274,
8764-8769)
copyright 1999.
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Secondary reference #1
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Title
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Specific inhibition of herpes virus replication by receptor-Mediated entry of an antiviral peptide linked to escherichia coli enterotoxin b subunit.
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Authors
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A.Marcello,
A.Loregian,
A.Cross,
H.Marsden,
T.R.Hirst,
G.Palù.
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Ref.
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Proc Natl Acad Sci U S A, 1994,
91,
8994-8998.
[DOI no: ]
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PubMed id
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Secondary reference #2
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Title
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Refined structure of escherichia coli heat-Labile enterotoxin, A close relative of cholera toxin.
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Authors
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T.K.Sixma,
K.H.Kalk,
B.A.Van zanten,
Z.Dauter,
J.Kingma,
B.Witholt,
W.G.Hol.
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Ref.
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J Mol Biol, 1993,
230,
890-918.
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PubMed id
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