Induction of nonbilayer structures in diacylphosphatidylcholine model membranes by transmembrane alpha-helical peptides: Importance of hydrophobic mismatch and proposed role of tryptophans
Induction of nonbilayer structures in diacylphosphatidylcholine model membranes by transmembrane alpha-helical peptides: Importance of hydrophobic mismatch and proposed role of tryptophans
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DOI：
10.1021/bi9519258
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发表时间：
1996-01-23
期刊：
影响因子：
2.9
通讯作者：
Greathouse, DV
中科院分区：
文献类型：
--
作者：
Killian, JA;Salemink, I;Greathouse, DV
我们研究了几种疏水多肽对不同酰基链长的二酰基磷脂酰胆碱相行为的影响。这些多肽是不带电荷的，由一段长度可变的亮氨酸和丙氨酸交替序列组成，两侧有两个双链，N-和C-末端被封闭。首先，圆二色性测量表明，这些肽在二肉豆蔻酰磷脂酰胆碱的双层中采用跨膜取向的Ct-螺旋构象。随后的P-31 NMR测量表明，肽可以影响脂质组织，这取决于在液晶相中肽和脂质双层之间的疏水长度的差异。当17个氨基酸残基的长肽（WALP 17）以1/10的肽与脂质的摩尔比掺入时，在含有12和14个C原子的酰基链的饱和磷脂中维持双层，在16个C原子处形成各向同性相，并且在18和20个C原子处形成倒六方（H-II）相。对于19个氨基酸残基的长肽（WALP 19），观察到脂质相行为的类似变化，但是在长2个C原子的酰基链长度处。此外，在几个顺式不饱和磷脂酰胆碱模型膜，它被发现，这些肽和较短的类似物（WALP 16）诱导形成的非双层结构的疏水性错配的结果。有人提出，这种独特的能力的肽诱导磷脂酰胆碱模型膜中的非双层结构是由于存在两个dichans在膜/水界面的两侧，防止肽聚集时，错配增加。双层的疏水长度与不同肽的长度的比较表明，它是确定优选的脂质组织是否是双层，各向同性相，或Hn相的错配的精确程度。含肽双层和H！I相进一步表征后，WALP 16和二油酰磷脂酰胆碱的混合物的蔗糖密度梯度离心。分离的级分的P-31 NMR测量显示获得了两种组分的完全分离。对具有不同肽浓度的样品中的这些级分的化学分析表明，H-II相高度富集肽（肽/脂质摩尔比为1/6），而肽在脂质双层中的最大溶解度为约1/24（肽/脂质，摩尔）。肽诱导的HII阶段的分子模型，是迄今为止所获得的结果相一致。
We have investigated the effect of several hydrophobic polypeptides on the phase behavior of diacylphosphatidylcholines with different acyl chain length, The polypeptides are uncharged and consist of a sequence with variable length of alternating leucine and alanine, flanked on both sides by two tryptophans, and with the N- and C-termini blocked. First it was demonstrated by circular dichroism measurements that these peptides adopt an ct-helical conformation with a transmembrane orientation in bilayers of dimyristoylphosphatidylcholine. Subsequent P-31 NMR measurements showed that the peptides can affect lipid organization depending on the difference in hydrophobic length between the peptide and the lipid bilayer in the liquid-crystalline phase. When a 17 amino acid residue long peptide (WALP17) was incorporated in a 1/10 molar ratio of peptide to lipid, a bilayer was maintained in saturated phospholipids containing acyl chains of 12 and 14 C atoms, an isotropic phase was formed at 16 C atoms, and an inverted hexagonal (H-II) phase at 18 and 20 C atoms. For a 19 amino acid residue long peptide (WALP19) similar changes in lipid phase behavior were observed, but at acyl chain lengths of 2 C-atoms longer. Also in several cis-unsaturated phosphatidylcholine model membranes it was found that these peptides and a shorter analog (WALP16) induce the formation of nonbilayer structures as a consequence of hydrophobic mismatch. It is proposed that this unique ability of the peptides to induce nonbilayer structures in phosphatidylcholine model membranes is due to the presence of two tryptophans at both sides of the membrane/water interface, which prevent the peptide from aggregating when the mismatch is increased. Comparison of the hydrophobic length of the bilayers with the length of the different peptides showed that it is the precise extent of mismatch that determines whether the preferred lipid organization is a bilayer, isotropic phase, or Hn phase. The peptide-containing bilayer and H!I phase were further characterized after sucrose density gradient centrifugation of mixtures of WALP16 and dioleoylphosphatidylcholine. P-31 NMR measurements of the isolated fractions showed that a complete separation of both components was obtained. Chemical analysis of these fractions in samples with varying peptide concentration indicated that the H-II phase is highly enriched in peptide (peptide/lipid molar ratio of 1/6), while the maximum solubility of the peptide in the lipid bilayer is about 1/24 (peptide/lipid, molar). A molecular model of the peptide-induced HII phase is presented that is consistent with the results obtained thus far.