PMID: 8464908Apr 1, 1993Paper

Experimental resolution of the free energies of aqueous solvation contributions to ligand-protein binding: quinone-QA site interactions in the photosynthetic reaction center protein

Proceedings of the National Academy of Sciences of the United States of America
K Warncke, P L Dutton

Abstract

Equilibrium binding free energies of 14 benzo-, naphtho-, and anthraquinone cofactors have been determined at the QA redox catalytic site of the purified photosynthetic reaction center protein from Rhodobacter sphaeroides solubilized in water (delta G degrees B,w), in hexane solution containing 30 mM water (delta G degrees B,hh), and after partial dehydration (delta G degrees B,dh) with magnesium sulfate. Our aim is to resolve the contributions of aqueous bulk phase solvation and protein hydration contributions to binding in order to characterize in detail the direct interactions between the ligands and protein at the QA site. This is accomplished by comparing the differences between delta G degrees B,w and delta G degrees B,hh (or delta G degrees B,dh) with the water to hexane solvent transfer free energies of the quinones (delta G degrees tr,Q). Values of delta G degrees tr,Q are determined separately in binary solution and range from 0.65 to -5.69 kcal/mol (1 cal = 4.184 J). The results are interpreted in terms of a thermodynamic cycle that links the species involved in the binding and solvent transfer equilibria. Values of delta G degrees B,hh -delta G degrees B,w are linearly correlated with -delta G degrees tr,Q (slope, 0...Continue Reading

References

Nov 9, 1978·Biochimica Et Biophysica Acta·R K Clayton
Sep 1, 1975·Proceedings of the National Academy of Sciences of the United States of America·M Y OkamuraG Feher
Aug 1, 1989·Proceedings of the National Academy of Sciences of the United States of America·A WarshelS Creighton
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Aug 1, 1971·Proceedings of the National Academy of Sciences of the United States of America·M I Page, W P Jencks

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Citations

Aug 17, 2005·Biochemistry·Jennifer Madeo, M R Gunner
Oct 25, 1994·Proceedings of the National Academy of Sciences of the United States of America·P L Dutton, C C Mosser
Jun 25, 1996·Proceedings of the National Academy of Sciences of the United States of America·R M XuX Cheng
May 8, 2001·Annual Review of Biophysics and Biomolecular Structure·K H Rhee

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