Thermodynamics of phosphorylcholine and lysophosphatidylcholine binding to the major protein of bovine seminal plasma, PDC-109 |
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Authors: | Anbazhagan V Swamy Musti J |
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Affiliation: | School of Chemistry, University of Hyderabad, India. |
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Abstract: | PDC-109 binds to sperm plasma membranes by specific interaction with choline phospholipids and induces cholesterol efflux, a necessary event before capacitation - and subsequent fertilization - can occur. The binding of phosphorylcholine (PrC) and lysophosphatidylcholine (Lyso-PC) with PDC-109 was investigated by monitoring the ligand-induced changes in the absorption spectrum of PDC-109. At 20 degrees C, the association constants (K(a)), for PrC and Lyso-PC were obtained as 81.4M(-1) and 2.02 x 10(4) M(-1), respectively, indicating that the binding of Lyso-PC to PDC-109 is 250-fold stronger than that of PrC. From the temperature dependence of the K(a) values, enthalpy of binding (DeltaH(0)) and entropy of binding (DeltaS(0)), were obtained as -79.7 and -237.1 J mol(-1)K(-1) for PrC and -73.0 kJ mol(-1) and -167.3 J mol(-1)K(-1) for Lyso-PC, respectively. These results demonstrate that although the binding of these two ligands is driven by enthalpic forces, smaller negative entropy of binding associated with Lyso-PC results in its significantly stronger binding. |
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Keywords: | Bovine seminal plasma proteins-A1/A2 Cholesterol efflux Choline phospholipid Binding enthalpy Binding entropy |
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