 |
PDBsum entry 2jml
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Transcription
|
PDB id
|
|
|
|
2jml
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Structural basis for operator and antirepressor recognition by myxococcus xanthus cara repressor.
|
|
|
Authors
|
|
G.Navarro-Avilés,
M.A.Jiménez,
M.C.Pérez-Marín,
C.González,
M.Rico,
F.J.Murillo,
M.Elías-Arnanz,
S.Padmanabhan.
|
|
|
Ref.
|
|
Mol Microbiol, 2007,
63,
980-994.
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
Blue light induces carotenogenesis in Myxococcus xanthus. The carB operon
encodes all but one of the structural genes involved, and its expression is
regulated by the CarA-CarS repressor-antirepressor pair. In the dark,
CarA-operator binding represses carB. CarS, produced on illumination, interacts
physically with CarA to dismantle the CarA-operator complex and activate carB.
Both operator and CarS bind to the autonomously folded N-terminal domain of
CarA, CarA(Nter), which in excess represses carB. Here, we report the NMR
structure of CarA(Nter), and map residues that interact with operator and CarS
by NMR chemical shift perturbations, and in vivo and in vitro analyses of
site-directed mutants. We show CarA(Nter) adopts the winged-helix topology of
MerR-family DNA-binding domains, and conserves the majority of the
helix-turn-helix and wing contacts with DNA. Tellingly, helix alpha2 in CarA, a
key element in operator DNA recognition, is also critical for interaction with
CarS, implying that the CarA-CarS protein-protein and the CarA-operator
protein-DNA interfaces overlap. Thus, binding of CarA to operator and to
antirepressor are mutually exclusive, and CarA may discern structural features
in the acidic CarS protein that resemble operator DNA. Repressor inactivation by
occluding the DNA-binding region may be a recurrent mechanism of action for
acidic antirepressors.
|
|
|
|
|
|
|
