Rao N M, Sundaram C S
Centre for Cellular and Molecular Biology, Hyderabad, India.
Biochemistry. 1993 Aug 24;32(33):8547-52. doi: 10.1021/bi00084a022.
We have recently demonstrated that phospholipase C (PLC) activity on membranes decreases in the presence of membrane-active peptides such as alamethicin, gramicidin S, and melittin [Rao, N. M. (1992) Biochem. Biophys. Res. Commun. 182, 682-688]. Since these peptides affect lipid packing in the membrane and induce nonbilayer phases depending on the lipid composition, we tested for the sensitivity of PLC activity to lipid packing. We monitored PLC activities on four lipid systems which demonstrate a transition from the bilayer to the nonbilayer phase as a function of one of the components. The four model systems are (1) dioleoylphosphatidylcholine (DOPC) and dioleoylphosphatidylethanolamine (DOPE); (2) DOPE, DOPC, and cholesterol; (3) DOPE and lysophosphatidylcholine; and (4) DOPC and gramicidin D. On all four lipid systems, the PLC activity was high for lipid in the bilayer phase and decreased as the phase changed to the nonbilayer phase. The phase changes were also monitored in PLC assay conditions on the four model systems by 31P NMR to confirm the observations made with PLC. These results suggest that the lipid in bilayer and nonbilayer phases was differentially susceptible to PLC; hence, PLC activity may be used to monitor isothermal phase transitions at physiological conditions.
我们最近证明，在诸如短杆菌肽A、短杆菌肽S和蜂毒肽等膜活性肽存在的情况下，膜上的磷脂酶C（PLC）活性会降低[Rao, N. M. (1992) Biochem. Biophys. Res. Commun. 182, 682 - 688]。由于这些肽会影响膜中的脂质堆积，并根据脂质组成诱导非双层相，我们测试了PLC活性对脂质堆积的敏感性。我们监测了四种脂质体系上的PLC活性，这四种脂质体系会随着其中一种成分的变化而呈现从双层相到非双层相的转变。这四种模型体系分别是：（1）二油酰磷脂酰胆碱（DOPC）和二油酰磷脂酰乙醇胺（DOPE）；（2）DOPE、DOPC和胆固醇；（3）DOPE和溶血磷脂酰胆碱；（4）DOPC和短杆菌肽D。在所有这四种脂质体系上，双层相脂质的PLC活性较高，并且随着相转变为非双层相而降低。在PLC分析条件下，还通过31P NMR监测了这四种模型体系的相变化，以证实用PLC所做的观察结果。这些结果表明，双层相和非双层相中的脂质对PLC的敏感性不同；因此，PLC活性可用于监测生理条件下的等温相变。
