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Title
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UV and X-ray structural studies of a 101-residue long Tat protein from a HIV-1 primary isolate and of its mutated, detoxified, vaccine candidate.
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Authors
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M.Foucault,
K.Mayol,
V.Receveur-Bréchot,
M.C.Bussat,
C.Klinguer-Hamour,
B.Verrier,
A.Beck,
R.Haser,
P.Gouet,
C.Guillon.
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Ref.
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Proteins, 2010,
78,
1441-1456.
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PubMed id
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Abstract
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The 101-residue long Tat protein of primary isolate 133 of the human
immunodeficiency virus type 1 (HIV-1), wt-Tat(133) displays a high
transactivation activity in vitro, whereas the mutant thereof, STLA-Tat(133), a
vaccine candidate for HIV-1, has none. These two proteins were chemically
synthesized and their biological activity was validated. Their structural
properties were characterized using circular dichroism (CD), fluorescence
emission, gel filtration, dynamic light scattering, and small angle X-ray
scattering (SAXS) techniques. SAXS studies revealed that both proteins were
extended and belong to the family of intrinsically unstructured proteins. CD
measurements showed that wt-Tat(133) or STLA-Tat(133) underwent limited
structural rearrangements when complexed with specific fragments of antibodies.
Crystallization trials have been performed on the two forms, assuming that the
Tat(133) proteins might have a better propensity to fold in supersaturated
conditions, and small crystals have been obtained. These results suggest that
biologically active Tat protein is natively unfolded and requires only a limited
gain of structure for its function.
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