CprK crystal structures reveal mechanism for transcriptional control of halorespiration.

M Gordon Joyce, Colin Levy, Krisztina Gábor, Stelian M Pop, Benjamin D Biehl, Tzanko I Doukov, Jodi M Ryter, Hortense Mazon, Hauke Smidt, Robert H H van den Heuvel, Stephen W Ragsdale, John van der Oost, David Leys

Index: J. Biol. Chem. 281(38) , 28318-25, (2006)

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Abstract

Halorespiration is a bacterial respiratory process in which haloorganic compounds act as terminal electron acceptors. This process is controlled at transcriptional level by CprK, a member of the ubiquitous CRP-FNR family. Here we present the crystal structures of oxidized CprK in presence of the ligand ortho-chlorophenolacetic acid and of reduced CprK in absence of this ligand. These structures reveal that highly specific binding of chlorinated, rather than the corresponding non-chlorinated, phenolic compounds in the NH(2)-terminal beta-barrels causes reorientation of these domains with respect to the central alpha-helix at the dimer interface. Unexpectedly, the COOH-terminal DNA-binding domains dimerize in the non-DNA binding state. We postulate the ligand-induced conformational change allows formation of interdomain contacts that disrupt the DNA domain dimer interface and leads to repositioning of the helix-turn-helix motifs. These structures provide a structural framework for further studies on transcriptional control by CRP-FNR homologs in general and of halorespiration regulation by CprK in particular.