Structures of three diphtheria toxin repressor (DtxR) variants with decreased repressor activity

Acta Crystallographica. Section D, Biological Crystallography
E PohlW G Hol

Abstract

The diphtheria toxin repressor (DtxR) from Corynebacterium diphtheriae regulates the expression of the gene on corynebacteriophages that encodes diphtheria toxin (DT). Other genes regulated by DtxR include those that encode proteins involved in siderophore-mediated iron uptake. DtxR requires activation by divalent metals and holo-DtxR is a dimeric regulator with two distinct metal-binding sites per three-domain monomer. At site 1, three side chains and a sulfate or phosphate anion are involved in metal coordination. In the DtxR-DNA complex this anion is replaced by the side chain of Glu170 provided by the third domain of the repressor. At site 2 the metal ion is coordinated exclusively by constituents of the polypeptide chain. In this paper, five crystal structures of three DtxR variants focusing on residues Glu20, Arg80 and Cys102 are reported. The resolution of these structures ranges from 2.3 to 2.8 A. The side chain of Glu20 provided by the DNA-binding domain forms a salt bridge to Arg80, which in turn interacts with the anion. Replacing either of the salt-bridge partners with an alanine reduces repressor activity substantially and it has been inferred that the salt bridge could possibly control the wedge angle between the ...Continue Reading

Citations

Jun 3, 2010·Acta Crystallographica. Section F, Structural Biology and Crystallization Communications·Yi Che SuShan Ho Chou
Dec 15, 2005·Proceedings of the National Academy of Sciences of the United States of America·J Alejandro D'AquinoDagmar Ringe
Sep 27, 2001·Proceedings of the National Academy of Sciences of the United States of America·P D TwiggD L Caspar
Apr 20, 2004·Current Opinion in Structural Biology·Christine VogelSarah A Teichmann

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