Zschörnig O, Paasche G, Thieme C, Korb N, Fahrwald A, Arnold K
University of Leipzig, Institute for Medical Physics and Biophysics, FRG.
Gen Physiol Biophys. 2000 Mar;19(1):85-101.
Lysozyme is a globular protein which is known to bind to negatively charged phospholipid vesicles. In order to study the relationship between binding of the protein and the subsequent destabilization of the phospholipid vesicles a set of experiments was performed using phospholipid monolayers and vesicles. Using microelectrophoresis the binding of lysozyme to phospholipid vesicles made of PS was determined. At low ionic strength and mild acidic pH of the solution lysozyme reduced the magnitude of the negative zeta potential of PS vesicles at lower concentrations compared to neutral pH and high ionic strength. In contrast, the bound fraction of lysozyme to PS vesicles was nearly constant at acidic and neutral pH. At low pH, the binding of lysozyme was accompanied by a strong aggregation of the vesicles. Lysozyme binding to PS vesicles is accompanied by its penetration into the PL monolayer. This was measured by surface tension and film balance measurements at low pH and low ionic strength. The interaction of lysozyme with negatively charged vesicles lead to a decrease of the vesicle surface hydration as measured by the shift of the emission peak of the fluorescent probe DPE. The binding of bis-ANS increased at low pH after addition of lysozyme to the vesicles. This indicates that more hydrophobic patches of the lysozyme-PS complex are exposed at low pH. At low pH the binding process of lysozyme to PS vesicles was followed by an extensive intermixing of phospholipids between the aggregated vesicles, accompanied by a massive leakage of the aqueous content of vesicles.
溶菌酶是一种已知能与带负电荷的磷脂囊泡结合的球状蛋白质。为了研究该蛋白质的结合与磷脂囊泡随后的去稳定化之间的关系，使用磷脂单层和囊泡进行了一组实验。通过微电泳测定了溶菌酶与由磷脂酰丝氨酸（PS）制成的磷脂囊泡的结合。在低离子强度和溶液的轻度酸性pH条件下，与中性pH和高离子强度相比，溶菌酶在较低浓度时就降低了PS囊泡负zeta电位的幅度。相反，溶菌酶与PS囊泡的结合分数在酸性和中性pH下几乎恒定。在低pH时，溶菌酶的结合伴随着囊泡的强烈聚集。溶菌酶与PS囊泡的结合伴随着其渗透到磷脂单层中。这是在低pH和低离子强度下通过表面张力和膜平衡测量来测定的。溶菌酶与带负电荷囊泡的相互作用导致囊泡表面水合作用降低，这通过荧光探针二苯基己三烯（DPE）发射峰的移动来测量。在向囊泡中加入溶菌酶后，双-ANS（bis-ANS）的结合在低pH时增加。这表明溶菌酶-PS复合物在低pH时暴露出更多的疏水区域。在低pH时，溶菌酶与PS囊泡的结合过程之后是聚集囊泡之间磷脂的广泛混合，同时伴随着囊泡内水溶液的大量泄漏。
