Calorimetric studies of the energetics of protein—DNA interactions in the E. coli methionine repressor (MetJ) system
- 4 July 1994
- journal article
- Published by Wiley in FEBS Letters
- Vol. 348 (1) , 41-45
- https://doi.org/10.1016/0014-5793(94)00579-6
Abstract
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.Keywords
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