物理化学学报 >> 2015, Vol. 31 >> Issue (10): 1985-1990.doi: 10.3866/PKU.WHXB201508262

生物物理化学 上一篇    下一篇

多肽诱导的巨型脂质体出芽和泄露行为

孙建波,夏玉琼,于秋红,梁德海*()   

  • 收稿日期:2015-05-04 发布日期:2015-10-10
  • 通讯作者: 梁德海 E-mail:dliang@pku.edu.cn
  • 基金资助:
    国家自然科学基金(21074005, 21174007)

Peptide-Induced Budding and Leakage Behavior of Giant Vesicles

Jian-Bo. SUN,Yu-Qiong. XIA,Qiu-Hong. YU,De-Hai. LIANG*()   

  • Received:2015-05-04 Published:2015-10-10
  • Contact: De-Hai. LIANG E-mail:dliang@pku.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21074005, 21174007)

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摘要：

细胞膜与膜蛋白之间的相互作用与生命中许多过程息息相关.以巨型脂质体(GUV)和多肽分别作为细胞膜和膜蛋白的简化模型,我们设计了四种仅包含亮氨酸(L)和赖氨酸(K)的多肽,即K14、(KL2KL2K)2、(KL2KL3)2和K6L8,并对比研究了它们与中性和负电性脂质体的相互作用.电荷密度最高的K14只是涂层在脂质体表面,不破其囊泡结构,但能够引起负电性脂质体发生微相分离,属建设性相互作用.能够形成两亲性α螺旋的(KL2KL2K)2和(KL2KL3)2则引起脂质体发生泄露和破裂,属破坏性作用.但二者引起泄露的速率在中性脂质体和负电性脂质体中的结果恰好相反,说明泄露分两步进行:表面吸附多肽达到一定浓度,继而对膜进行干扰.表面活性剂型多肽K6L8的氨基酸组成与(KL2KL2K)2相同,但K6L8只是引起负电性脂质体发生泄露,造成中性脂质体发生外出芽.这些简单氨基酸造成的脂质体的复杂构象变化可以统一用静电和疏水相互作用在膜上的位置和强度来进行解释.这些结论对于深入理解膜蛋白的作用机理是有帮助的.

关键词: 多肽, 巨型脂质体, 出芽, 泄露

Abstract:

The interactions between membrane proteins and cell membranes are critical in many life processes. Giant unilamellar vesicles (GUVs) and peptides are simple but effective models of membranes and membrane proteins, respectively. Here, we designed four peptides composed of lysine (K) and leucine (L) amino acids, K14, (KL2KL2K)2, (KL2KL3)2, and K6L8, and examined their interactions with neutral and negatively charged GUVs. The peptide K14 has the largest charge density and is able to coat the GUV surface without damaging its structure. Whereas, leakage is observed in both neutral and charged GUVs in the presence of (KL2KL2K)2 and (KL2KL3)2, which can form amphiphilic α-helices in hydrophobic environments. However, the leakage rates as a function of peptide concentration are reversed for the neutral and charged GUVs. Thus, leakage occurs in two steps: absorption of peptides on the surface up to a certain level, followed by disruption of the membrane. The peptide K6L8 has the same chemical composition as (KL2KL2K)2, but induces leakage only on negatively charged GUVs, while neutral GUVs undergo outward budding. Conformational changes of GUVs induced by simple peptides can be attributed to the working location (on the surface or inside the membrane), and the strength of electrostatic and hydrophobic interactions. Overall, the results provide a better understanding of membrane protein mechanisms.

Key words: Peptide, Giant vesicle, Budding, Leakage