YbiB from XXXX - the defining member of the novel TrpD2 family of prokaryotic DNA binding proteins.

@entity73114 @entity4561 @entity19727 @entity8742 @entity526
UNASSIGNED: We present the crystal structure and biochemical characterisation of @entity526 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 @entity19727 phosphoribosyltransferase (TrpD) and @entity8742 phosphorylase class II enzymes, but bind with high affinity ( @entity4561 = 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 monomerised variant remains able to bind DNA with similar affinity, but the negative cooperative effect is eliminated. The ybiB gene forms an operon with the @entity73114 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.
