Gawrisch K, Barry J A, Holte L L, Sinnwell T, Bergelson L D, Ferretti J A
Laboratory of Membrane Biochemistry and Biophysics, NIAAA, NIH, Rockville, MD 20852, USA.
Mol Membr Biol. 1995 Jan-Mar;12(1):83-8. doi: 10.3109/09687689509038500.
The lipid-water interface is critical for the packing of lipid molecules in membranes. We have demonstrated that lateral phase separation in membranes can be driven by electrostatic interactions such as those involving charged lipid species and oppositely charged peptides, in addition to hydration effects at the lipid-water interface. By using nuclear magnetic resonance (NMR), circular dichroism and fluorescence spectroscopy we have shown that binding of a 21-amino acid peptide containing six positively charged arginine residues to mixed phosphatidylcholine (PC)/phosphatidylglycerol (PG) membranes results in a conformational change in the peptide from a random coil to a helical structure and causes the formation of domains of negatively charged PG. Binding of the peptide to PG membranes disorders the lipid hydrocarbon chains. The strength of lipid-peptide binding at the interface, the conformational change in the peptide, and domain formation with the negatively charged lipid are coupled energetically. The lipid-peptide association constant is lower for membranes containing 20 mol% PG in PC/PG mixtures than for 100% PG membranes. We suggest that one of the factors that lower the association constant in PC/PG membranes is entropic energy of formation of PG domains. Besides electrostatic interactions, hydration of lipids is important for domain formation. We have shown that dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylethanolamine separate under conditions of decreased water activity. Furthermore, water activity controls lipid packing stress in the hydrocarbon core and the headgroups of membranes as demonstrated by induction of an inverse-hexagonal-to-lamellar phase transition in dioleoylphosphatidylethanolamine.(ABSTRACT TRUNCATED AT 250 WORDS)
脂质 - 水界面对于脂质分子在膜中的堆积至关重要。我们已经证明，除了脂质 - 水界面的水合作用外，膜中的横向相分离可由静电相互作用驱动，例如涉及带电脂质种类和带相反电荷肽的相互作用。通过使用核磁共振（NMR）、圆二色性和荧光光谱，我们表明，一种含有六个带正电荷精氨酸残基的21个氨基酸的肽与混合磷脂酰胆碱（PC）/磷脂酰甘油（PG）膜的结合会导致肽的构象从无规卷曲转变为螺旋结构，并导致带负电荷的PG形成结构域。肽与PG膜的结合会扰乱脂质烃链。界面处脂质 - 肽结合的强度、肽的构象变化以及与带负电荷脂质形成的结构域在能量上是相互关联的。在PC/PG混合物中含有20摩尔％PG的膜的脂质 - 肽缔合常数低于100％PG膜。我们认为，降低PC/PG膜中缔合常数的因素之一是PG结构域形成的熵能。除了静电相互作用外，脂质的水合作用对于结构域形成也很重要。我们已经表明，二棕榈酰磷脂酰胆碱和二棕榈酰磷脂酰乙醇胺在水活性降低的条件下会分离。此外，水活性控制膜烃核和头部基团中的脂质堆积应力，如在二油酰磷脂酰乙醇胺中诱导反六角形到层状相转变所证明的那样。（摘要截断于250字）
