Thermodynamics of nucleotide binding to NBS‐I of the Bacillus subtilis preprotein translocase subunit SecA
- 10 September 1999
- journal article
- Published by Wiley in FEBS Letters
- Vol. 458 (2) , 145-150
- https://doi.org/10.1016/s0014-5793(99)01139-4
Abstract
SecA is the dissociatable nucleotide and preprotein binding subunit of the bacterial translocase. The thermodynamics of nucleotide binding to soluble SecA at nucleotide binding site I were determined by isothermal titration calorimetry. Binding of ADP and non-hydrolyzable ATPγS is enthalpy-driven (ΔH 0 of −14.44 and −5.56 kcal/mol, respectively), but is accompanied by opposite entropic contributions (ΔS 0 of −18.25 and 9.55 cal/mol/K, respectively). ADP binding results in a large change in the heat capacity of SecA (ΔC p=−780 cal/mol/K). It is suggested that ADP binding promotes the interaction between the two thermodynamically discernible domains of SecA which is accompanied by a shielding of hydrophobic surface from solvent.Keywords
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