Calorimetric studies of the energetics of protein—DNA interactions in the E. coli methionine repressor (MetJ) system

FEBS Letters

Cooper, Alan¹  Stockley, Peter G.²  McAlpine, Alan¹ 

[1] Department of Chemistry, Glasgow University, Glasgow, G12 8QQ, Scotland, UK;Department of Genetics, University of Leeds, Leeds, LS2 9JT UK

关键词: Protein-DNA interaction;    Calorimetry;    Energetics;    Dynamics;    Methionine repressor;   

DOI  :  10.1016/0014-5793(94)00579-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Calorimetric measurements of binding of a specific DNA fragment and S-adenosyl methionine (SAM) co-repressor molecules to the E. coli methionine repressor (MetJ) show significant differences in the energetics of binary and ternary protein-DNA complexes. Formation of the MetJ: SAM: DNA ternary complex is significantly more exothermic (ΔH ⋍ −99 kJ·mol⁻¹) than either MetJ:DNA or MetJ:SAM binary complexes alone (ΔH ⋍ −10 kJ·mol⁻¹ each). The protein is also significantly more stable to unfolding (ΔT _m ⋍ 5.4°C) when bound to DNA. These observations suggest that binding of SAM to the protein-DNA complex leads to a significant reduction in dynamic flexibility of the ternary complex, with considerable entropy-enthalpy compensation, not necessarily involving any overall conformational change.

【 授权许可】

Unknown