title: Thermodynamics of nucleotide binding to NBS-I of the Bacillus subtilis preprotein translocase subunit SecA.
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 ATPgammaS is enthalpy-driven (DeltaH(0) of -14.44 and -5.56 kcal/mol, respectively), but is accompanied by opposite entropic contributions (DeltaS(0) of -18.25 and 9.55 cal/mol/K, respectively). ADP binding results in a large change in the heat capacity of SecA (DeltaC(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.
authors.affiliation: Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands.
authors.forename: T
authors.initials: T
authors.lastname: den Blaauwen
authors.forename: J P
authors.initials: JP
authors.lastname: van der Wolk
authors.forename: C
authors.initials: C
authors.lastname: van der Does
authors.forename: K H
authors.initials: KH
authors.lastname: van Wely
authors.forename: A J
authors.initials: AJ
authors.lastname: Driessen
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism*; D001412:Bacillus subtilis / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D001692:Biological Transport; D002152:Calorimetry, Differential Scanning; D004792:Enzyme Precursors / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D008956:Models, Chemical; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D004792:Enzyme Precursors; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D010446:Peptide Fragments; D000069816:SEC Translocation Channels; C022571:adenosine 5'-O-(3-thiotriphosphate); D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins