Experimental evidence for hydrophobic matching and membrane-mediated interactions in lipid bilayers containing gramicidin
Experimental evidence for hydrophobic matching and membrane-mediated interactions in lipid bilayers containing gramicidin
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DOI：
10.1016/s0006-3495(99)77257-7
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发表时间：
1999-02-01
影响因子：
3.4
通讯作者：
Huang, HW
中科院分区：
文献类型：
--
作者：
Harroun, TA;Heller, WT;Huang, HW
疏水匹配，其中跨膜蛋白引起周围的脂质双层调整其烃厚度以匹配蛋白质的疏水表面的长度，是膜生物物理学中普遍接受的想法。为了测试这个想法，短杆菌肽（gD）以1：10的肽/脂质摩尔比包埋在1，2-二月桂酰-sn-甘油基-3-磷酸胆碱（DLPC）和1，2-肉豆蔻酰-sn-甘油基-3-磷酸胆碱（DMPC）双层中。测量圆二色性（CD）以确保短杆菌肽为β（6.3）螺旋形式。通过X射线层状衍射测量双层厚度（磷酸盐-磷酸盐距离，或PtP）。在接近完全水合的L-α相中，纯DLPC的PtP为30.8埃，DLPC/gD混合物为32.1埃，纯DMPC为35.3埃，DMPC/gD混合物为32.7埃。短杆菌肽明显地拉伸DLPC并使DMPC向疏水匹配所预期的共同厚度变薄。同时，短杆菌肽-短杆菌肽相关性通过X射线平面内散射测量。在液相中，短杆菌肽-短杆菌肽最近邻分离在DLPC中为26.8埃，而在DMPC中缩短至23.3埃。这些实验证实了这样的猜想，即当蛋白质嵌入膜中时，疏水匹配在脂质双层中产生应变场，这反过来又引起蛋白质之间的膜介导的吸引力。
Hydrophobic matching, in which transmembrane proteins cause the surrounding lipid bilayer to adjust its hydrocarbon thickness to match the length of the hydrophobic surface of the protein, is a commonly accepted idea in membrane biophysics. To test this idea, gramicidin (gD) was embedded in 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) and 1,2-myristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers at the peptide/lipid molar ratio of 1:10. Circular dichroism (CD) was measured to ensure that the gramicidin was in the beta(6.3) helix form, The bilayer thickness (the phosphate-to-phosphate distance, or PtP) was measured by x-ray lamellar diffraction. In the L-alpha phase near full hydration, PtP is 30.8 Angstrom for pure DLPC, 32.1 Angstrom for the DLPC/gD mixture, 35.3 Angstrom for pure DMPC, and 32.7 Angstrom for the DMPC/gD mixture. Gramicidin apparently stretches DLPC and thins DMPC toward a common thickness as expected by hydrophobic matching. Concurrently, gramicidin-gramicidin correlations were measured by x-ray in-plane scattering. In the fluid phase, the gramicidin-gramicidin nearest-neighbor separation is 26.8 Angstrom in DLPC, but shortens to 23.3 Angstrom in DMPC. These experiments confirm the conjecture that when proteins are embedded in a membrane, hydrophobic matching creates a strain field in the lipid bilayer that in turn gives rise to a membrane-mediated attractive potential between proteins.