Structure of the Branched Chain Amino Acid and GTP Sensing Global Regulator, CodY, from Bacillus subtilis

Vladimir M Levdikov, Elena V Blagova, Vicki L Young, Boris R Belitsky, Andrey Lebedev, Abraham L Sonenshein, Anthony J Wilkinson

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CodY is a branched-chain amino acid (BCAA) and GTP sensor, and a global regulator of transcription in low G + C Gram-positive bacteria. It controls the expression of over 100 genes and operons, principally by repressing during growth genes whose products are required for adaptations to nutrient limitation. CodY consists of a GAF domain that binds BCAAs and a winged helix-turn-helix (wHTH) domain that binds to DNA, but the way in which these domains interact and the structural basis of the BCAA-dependence of this interaction are unknown. To gain new insights, we determined the crystal structure of unliganded CodY from Bacillus subtilis revealing a 10-turn alpha-helix linking otherwise discrete GAF and wHTH domains. The structure of CodY in complex with isoleucine revealed a reorganised GAF domain. In both complexes CodY was tetrameric. Size exclusion chromatography with multiangle laser light scattering (SEC-MALLS) experiments showed that CodY is a dimer at concentrations found in bacterial cells. Comparison of structures of dimers of unliganded CodY and CodY-Ile derived from the tetramers showed a splaying of the wHTH domains when Ile was bound; splaying is likely to account for the increased affinity of Ile-bound CodY for DNA. Electrophoretic mobility shift and SEC-MALLS analyses of CodY binding to 19-36 base-pair operator fragment are consistent with isoleucine-dependent binding of two CodY dimers per duplex. The implications of these observations for effector control of CodY activity are discussed.

Original languageEnglish
Pages (from-to)1-36
Number of pages36
JournalThe Journal of biological chemistry
Early online date23 Dec 2016
Publication statusE-pub ahead of print - 23 Dec 2016

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Copyright 2016 by The American Society for Biochemistry and Molecular Biology, Inc. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.

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