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PDBsum entry 2ecs
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Transcription
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PDB id
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2ecs
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References listed in PDB file
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Key reference
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Title
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Two structures of a lambda cro variant highlight dimer flexibility but disfavor major dimer distortions upon specific binding of cognate DNA.
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Authors
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B.M.Hall,
S.A.Roberts,
A.Heroux,
M.H.Cordes.
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Ref.
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J Mol Biol, 2008,
375,
802-811.
[DOI no: ]
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PubMed id
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Abstract
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Previously reported crystal structures of free and DNA-bound dimers of lambda
Cro differ strongly (about 4 A backbone rmsd), suggesting both flexibility of
the dimer interface and induced-fit protein structure changes caused by
sequence-specific DNA binding. Here, we present two crystal structures, in space
groups P3(2)21 and C2 at 1.35 and 1.40 A resolution, respectively, of a variant
of lambda Cro with three mutations in its recognition helix (Q27P/A29S/K32Q, or
PSQ for short). One dimer structure (P3(2)21; PSQ form 1) resembles the
DNA-bound wild-type Cro dimer (1.0 A backbone rmsd), while the other (C2; PSQ
form 2) resembles neither unbound (3.6 A) nor bound (2.4 A) wild-type Cro. Both
PSQ form 2 and unbound wild-type dimer crystals have a similar interdimer
beta-sheet interaction between the beta1 strands at the edges of the dimer. In
the former, an infinite, open beta-structure along one crystal axis results,
while in the latter, a closed tetrameric barrel is formed. Neither the DNA-bound
wild-type structure nor PSQ form 1 contains these interdimer interactions. We
propose that beta-sheet superstructures resulting from crystal contact
interactions distort Cro dimers from their preferred solution conformation,
which actually resembles the DNA-bound structure. These results highlight the
remarkable flexibility of lambda Cro but also suggest that sequence-specific DNA
binding may not induce large changes in the protein structure.
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Figure 1.
Fig. 1. λ Cro dimer structures, including (a) the crystal
structure of wild-type Cro with symmetric cognate consensus DNA
(PDB ID 6CRO), (b) the crystal structure of free wild-type Cro
(5CRO), (c) the solution ensemble of free wild-type Cro (1COP),
and (d and e) the two forms of the PSQ Cro variant solved in the
present study. This figure was generated using PyMOL (DeLano
Scientific, San Carlos, CA).
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Figure 5.
Fig. 5. β-Sheet superstructures in the crystal structures of
(a) wild-type λ Cro (5CRO) and (b) PSQ form 2. The two views in
(a) illustrate the closed 12-stranded tetrametric β-barrel
formed by the two dimers in the asymmetric unit of the wild-type
λ Cro structure. (b) shows five symmetry-related dimers of PSQ,
which illustrate the infinite corkscrew of β-structure along
one crystal axis. The picture is oriented so that the leftmost
PSQ dimer in (b) may be compared to the wild-type dimer in the
foreground of the left half of (a). Each dimer in PSQ form 2
interacts with two other symmetry-related dimers, while in
wild-type Cro, each dimer interacts with only one other dimer.
Loops at the N- and C-termini of all structures are omitted for
clarity. This figure was generated using PyMOL.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2008,
375,
802-811)
copyright 2008.
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