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81 a.a.
Key reference
DOI no: 10.1111/j.1365-2958.2006.05567.x Mol Microbiol 63:980-994 (2007) PubMed id: 17233828
Structural basis for operator and antirepressor recognition by Myxococcus xanthus CarA repressor. G.Navarro-Avilés, M.A.Jiménez, M.C.Pérez-Marín, C.González, M.Rico, F.J.Murillo, M.Elías-Arnanz, S.Padmanabhan. 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.
Literature references that cite this PDB file's key reference
PubMed id Reference
19251845 D.García-Moreno, M.C.Polanco, G.Navarro-Avilés, F.J.Murillo, S.Padmanabhan, and M.Elías-Arnanz (2009).
A vitamin B12-based system for conditional expression reveals dksA to be an essential gene in Myxococcus xanthus.J Bacteriol, 191, 3108-3119.
19240136 N.Tschowri, S.Busse, and R.Hengge (2009).
The BLUF-EAL protein YcgF acts as a direct anti-repressor in a blue-light response of Escherichia coli.Genes Dev, 23, 522-534.
18310035 L.Galbis-Martínez, M.Galbis-Martínez, F.J.Murillo, and M.Fontes (2008).
An anti-antisigma factor in the response of the bacterium Myxococcus xanthus to blue light.Microbiology, 154, 895-904.
17921255 G.Chen, P.D.Jeffrey, C.Fuqua, Y.Shi, and L.Chen (2007).
Structural basis for antiactivation in bacterial quorum sensing.Proc Natl Acad Sci U S A, 104, 16474-16479.
PDB code: 2q0o The most recent references are shown first. Citation data come partly from CiteXplore and partly from an automated harvesting procedure. Note that this is likely to be only a partial list as not all journals are covered by either method. However, we are continually building up the citation data so more and more references will be included with time. Where a reference describes a PDB structure, the PDB code is shown on the right.
