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Thermodynamics of the DNA binding reaction of transcription factor MASH-1

Künne, Andreas G. E., Sieber, Martin, Meierhans, Daniel and Allemann, Rudolf Konrad 1998. Thermodynamics of the DNA binding reaction of transcription factor MASH-1. Biochemistry 37 (12) , pp. 4217-4223. 10.1021/bi9725374

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Abstract

MASH-1, a member of the basic helix−loop−helix (BHLH) family of transcription factors, promotes the differentiation of committed neuronal precursor cells. We have determined the thermodynamic parameters of the DNA binding reaction of the BHLH domain of MASH-1 (MASH−BHLH) by isothermal titration calorimetry and found that the specificity of the binding reaction was rather low. At 27 °C, the association constant for binding was 5.13 (±0.51) × 108 M-1 for an E-box containing oligonucleotide, while for a heterologous DNA sequence it was 5.14 (±1.93) × 107 M-1. The reaction enthalpy and the reaction entropy were strongly dependent on the temperature, but the reaction free energy was almost independent of temperature. The association reaction was enthalpically driven throughout the physiological temperature range and characterized by a large negative heat capacity change. No change in the protonation state of the protein and/or the DNA was observed at pH 6. Within experimental error, the reaction was independent of pH between pH 6 and 8. Dissection of the entropy change of the binding reaction indicated that binding was coupled to local protein folding of approximately 25 amino acids per protein subunit. The circular dichroism spectra of free and DNA-bound MASH−BHLH revealed the formation of additional α-helical structure comprising approximately 25 amino acids upon complex formation. Therefore, while the basic region was in an α-helical conformation in the DNA complex, in free MASH−BHLH it was substantially unfolded even at concentrations where the protein is mainly dimeric. The association between MASH-1 and DNA is therefore an example of “induced fit”.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Cardiff Catalysis Institute (CCI)
Subjects: Q Science > QD Chemistry
Publisher: American Chemical Society
ISSN: 0006-2960
Last Modified: 04 Jun 2017 02:53
URI: http://orca.cf.ac.uk/id/eprint/13464

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