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PDBsum entry 2m1b
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Transcription regulator
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PDB id
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2m1b
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References listed in PDB file
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Key reference
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Title
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Atypical response regulator chxr from chlamydia trachomatis is structurally poised for DNA binding.
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Authors
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M.L.Barta,
J.M.Hickey,
A.Anbanandam,
K.Dyer,
M.Hammel,
P.S.Hefty.
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Ref.
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Plos One, 2014,
9,
e91760.
[DOI no: ]
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PubMed id
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Abstract
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ChxR is an atypical two-component signal transduction response regulator (RR) of
the OmpR/PhoB subfamily encoded by the obligate intracellular bacterial pathogen
Chlamydia trachomatis. Despite structural homology within both receiver and
effector domains to prototypical subfamily members, ChxR does not require
phosphorylation for dimer formation, DNA binding or transcriptional activation.
Thus, we hypothesized that ChxR is in a conformation optimal for DNA binding
with limited interdomain interactions. To address this hypothesis, the NMR
solution structure of the ChxR effector domain was determined and used in
combination with the previously reported ChxR receiver domain structure to
generate a full-length dimer model based upon SAXS analysis. Small-angle
scattering of ChxR supported a dimer with minimal interdomain interactions and
effector domains in a conformation that appears to require only subtle
reorientation for optimal major/minor groove DNA interactions. SAXS modeling
also supported that the effector domains were in a head-to-tail conformation,
consistent with ChxR recognizing tandem DNA repeats. The effector domain
structure was leveraged to identify key residues that were critical for
maintaining protein - nucleic acid interactions. In combination with prior
analysis of the essential location of specific nucleotides for ChxR recognition
of DNA, a model of the full-length ChxR dimer bound to its cognate cis-acting
element was generated.
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