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Thermodynamics of nucleotide binding to NBS‐I of the Bacillus subtilis preprotein translocase subunit SecA
Author(s) -
den Blaauwen Tanneke,
van der Wolk Jeroen P.W.,
van der Does Chris,
van Wely Karel H.M.,
Driessen Arnold J.M.
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)01139-4
Subject(s) - translocase , isothermal titration calorimetry , nucleotide , bacillus subtilis , chemistry , protein subunit , binding site , biochemistry , calorimetry , crystallography , biology , thermodynamics , bacteria , genetics , chromosomal translocation , physics , gene
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 (Δ H 0 of −14.44 and −5.56 kcal/mol, respectively), but is accompanied by opposite entropic contributions (Δ S 0 of −18.25 and 9.55 cal/mol/K, respectively). ADP binding results in a large change in the heat capacity of SecA (Δ C 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.