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 (delta H congruent to -99 kJ.mol-1) than either MetJ:DNA or MetJ:SAM binary complexes alone (delta H congruent to -10 kJ.mol-1 each). The protein is also significantly more stable to unfolding (delta Tm congruent to 5.4 degrees 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. Study holds ProTherm entries: 10393 Extra Details: protein-DNA interaction; calorimetry; energetics; dynamics; methionine repressor
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:40 p.m.
|Number of data points||2|
|Proteins||Met repressor ; Met repressor|
|Assays/Quantities/Protocols||Experimental Assay: dHcal ; Experimental Assay: Tm|
|Libraries||Mutations for sequence AEWSGEYISPYAEHGKKSEQVKKITVSIPLKVLKILTDERTRRQVNNLRHATNSELLCEAFLHAFTGQPLPDDADLRKERSDEIPEAAKEIMREMGINPETWEY|