Thermodynamics of nucleotide binding to NBS-I of the Bacillus subtilis preprotein translocase subunit SecA.
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.
den Blaauwen
T
T
Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands.
van der Wolk
J P
JP
van der Does
C
C
van Wely
K H
KH
Driessen
A J
AJ
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
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