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PDBsum entry 1klr
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Transcription
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PDB id
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1klr
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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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The hidden thermodynamics of a zinc finger.
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Authors
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M.J.Lachenmann,
J.E.Ladbury,
N.B.Phillips,
N.Narayana,
X.Qian,
M.A.Weiss.
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Ref.
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J Mol Biol, 2002,
316,
969-989.
[DOI no: ]
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PubMed id
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Abstract
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The Zn finger provides a model for studies of protein structure and stability.
Its core contains a conserved phenylalanine residue adjoining three
architectural elements: a beta-hairpin, an alpha-helix and a tetrahedral
Zn(2+)-binding site. Here, we demonstrate that the consensus Phe is not required
for high-affinity Zn(2+) binding but contributes to the specification of a
precise DNA-binding surface. Substitution of Phe by leucine in a ZFY peptide
permits Zn(2+)-dependent folding. Although a native-like structure is retained,
structural fluctuations lead to attenuation of selected nuclear Overhauser
enhancements and accelerated amide proton exchange. Surprisingly, wild-type Zn
affinity is maintained by entropy-enthalpy compensation (EEC): a hidden entropy
penalty (TDeltaDeltaS 7kcal/mol) is balanced by enhanced enthalpy of association
(DeltaDeltaH -7kcal/mol) at 25 degrees C. Because the variant is less well
ordered than the Phe-anchored domain, the net change in entropy is opposite to
the apparent change in configurational entropy. By analogy to the thermodynamics
of organometallic complexation, we propose that EEC arises from differences in
solvent reorganization. Exclusion of Leu among biological sequences suggests an
evolutionary constraint on the dynamics of a Zn finger.
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Figure 1.
Figure 1. (a) A ribbon model of
the parent Zn finger showing Zn
2+
(blue sphere), ligands (two cysteine
and two histidine side-chains; light
blue), conserved leucine (L, light
blue), and central aromatic side-
chain (F10; red and asterisk). The C
terminus of the peptide is indi-
cated. (b) A CPK model of the
parent Zn finger showing the edge
of F10 in the potential crevice (dark
blue); the remainder of the surface
is shown in aquamarine. (c) A rep-
resentation of parent (F10) and
variant (L10) fingers. The side-
chains shown in (a) are shaded.
The numbering scheme refers
to the synthetic peptide (30
residues
19
). (d) CD spectra of Zn
2+
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free peptides (F10, continuous line;
and L10 dashed line) and Zn
2+
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bound peptides: wild-type (Phe;
filled circles) and variant (Leu;
open circles). CD spectra were
obtained at 25 ° C at a peptide con-
centration of 100 mM.
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Figure 3.
Figure 3. The 1D
1
H-NMR spec-
tra of the (a) parent Zn finger and
(b) variant Zn finger at 500 MHz
and 25 °C. Asterisks in (b) indicate
upfield methyl resonances of L10.
The upfield region of the wild-type
spectrum is remarkable for the
b-methylene protons of K25
(labeled in (a)). Arrow indicates
down-field amide resonance of
Y7, a characteristic feature of Zn
fingers.
17
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2002,
316,
969-989)
copyright 2002.
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Secondary reference #1
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Title
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Two-Dimensional nmr studies of the zinc finger motif: solution structures and dynamics of mutant zfy domains containing aromatic substitutions in the hydrophobic core.
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Authors
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X.Qian,
M.A.Weiss.
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Ref.
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Biochemistry, 1992,
31,
7463-7476.
[DOI no: ]
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PubMed id
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