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J Biol Chem. 2015 Aug 7;290(32):19527-39. doi: 10.1074/jbc.M114.620575. Epub 2015 Jun 10.

YbiB from Escherichia coli, the Defining Member of the Novel TrpD2 Family of Prokaryotic DNA-binding Proteins.

Author information

1
From the Institute of Biophysics and Physical Biochemistry, University of Regensburg, 93040 Regensburg, Germany.
2
the Division of Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland, and.
3
the Division of Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland, and the Institute of Integrative Biology, University of Liverpool, Crown Street, Liverpool L69 7ZB, United Kingdom.
4
From the Institute of Biophysics and Physical Biochemistry, University of Regensburg, 93040 Regensburg, Germany, patrick.babinger@ur.de.

Abstract

We present the crystal structure and biochemical characterization of Escherichia coli YbiB, a member of the hitherto uncharacterized TrpD2 protein family. Our results demonstrate that the functional diversity of proteins with a common fold can be far greater than predictable by computational annotation. The TrpD2 proteins show high structural homology to anthranilate phosphoribosyltransferase (TrpD) and nucleoside phosphorylase class II enzymes but bind with high affinity (KD = 10-100 nM) to nucleic acids without detectable sequence specificity. The difference in affinity between single- and double-stranded DNA is minor. Results suggest that multiple YbiB molecules bind to one longer DNA molecule in a cooperative manner. The YbiB protein is a homodimer that, therefore, has two electropositive DNA binding grooves. But due to negative cooperativity within the dimer, only one groove binds DNA in in vitro experiments. A monomerized variant remains able to bind DNA with similar affinity, but the negative cooperative effect is eliminated. The ybiB gene forms an operon with the DNA helicase gene dinG and is under LexA control, being induced by DNA-damaging agents. Thus, speculatively, the TrpD2 proteins may be part of the LexA-controlled SOS response in bacteria.

KEYWORDS:

DNA damage response; DNA-binding protein; cooperativity; crystallography; dimerization; functional annotation

PMID:
26063803
PMCID:
PMC4528117
DOI:
10.1074/jbc.M114.620575
[Indexed for MEDLINE]
Free PMC Article

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