Anbazhagan V, Swamy Musti J
School of Chemistry, University of Hyderabad, India.
FEBS Lett. 2005 May 23;579(13):2933-8. doi: 10.1016/j.febslet.2005.04.046.
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.
PDC - 109通过与胆碱磷脂的特异性相互作用结合到精子质膜上，并诱导胆固醇流出，这是获能以及随后受精能够发生之前的一个必要过程。通过监测配体诱导的PDC - 109吸收光谱变化，研究了磷酸胆碱（PrC）和溶血磷脂酰胆碱（Lyso - PC）与PDC - 109的结合情况。在20摄氏度时，PrC和Lyso - PC的缔合常数（K(a)）分别为81.4M(-1)和2.02×10(4) M(-1)，这表明Lyso - PC与PDC - 109的结合比PrC强250倍。根据K(a)值的温度依赖性，PrC的结合焓（DeltaH(0)）和结合熵（DeltaS(0)）分别为 - 79.7和 - 237.1 J mol(-1)K(-1)，Lyso - PC的分别为 - 73.0 kJ mol(-1)和 - 167.3 J mol(-1)K(-1)。这些结果表明，尽管这两种配体的结合是由焓力驱动的，但与Lyso - PC相关的较小负结合熵导致其结合力明显更强。
