Russell C J, Thorgeirsson T E, Shin Y K
Department of Chemistry, University of California, Berkeley 94720, USA.
Biochemistry. 1999 Jan 5;38(1):337-46. doi: 10.1021/bi981179h.
Understanding, predicting, and designing the binding of peptides and proteins to bilayers require quantifying the intrinsic propensities of individual amino acid residues to bind membranes as a function of structural context and bilayer depth. A host-guest study was performed using the peptide host named helix5 in order to determine the membrane affinities of the aliphatic side chains both in an alpha-helical context and as a function of bilayer depth. Use of the alpha-helical host with a constrained geometry allowed the placement of guest sites at three different depths in bilayers and minimized secondary structural changes due to guest substitutions. Circular dichroism and electron paramagnetic resonance (EPR) were used to characterize the aqueous and bilayer-bound structures of the peptide variants. EPR was also used to measure the bilayer-water partition constants of the peptide variants, and the Delta DeltaGtr values (relative to Gly) of the aliphatic amino acid side chains were subsequently calculated. Surprisingly, the DeltaDeltaGtr values did not significantly vary as a function of the guest site depth in bilayers. In addition, the Delta DeltaGtr values determined in an alpha-helical context are reduced to approximately two-thirds of Delta DeltaGtr values determined in other studies for the bilayer-water and octanol-water partitioning of amino acid side chains in extended and unstructured hosts. Both the relative reduction in Delta DeltaGtr values in the context of an alpha-helical host and the invariance of Delta DeltaGtr values with respect to bilayer depth are consistent with the membrane affinities of the aliphatic residues being largely determined by the classical hydrophobic effect.
理解、预测和设计肽与蛋白质与双层膜的结合需要量化单个氨基酸残基在不同结构背景和双层膜深度下与膜结合的内在倾向。为了确定脂肪族侧链在α-螺旋背景下以及作为双层膜深度的函数时的膜亲和力，使用名为helix5的肽主体进行了一项主客体研究。使用具有受限几何结构的α-螺旋主体可以将客体位点放置在双层膜的三个不同深度处，并使由于客体取代引起的二级结构变化最小化。圆二色性和电子顺磁共振（EPR）被用于表征肽变体的水溶液和双层膜结合结构。EPR还被用于测量肽变体的双层膜-水分配常数，随后计算脂肪族氨基酸侧链的ΔΔGtr值（相对于甘氨酸）。令人惊讶的是，ΔΔGtr值并没有随着双层膜中客体位点深度的变化而显著变化。此外，在α-螺旋背景下确定的ΔΔGtr值降低到了其他研究中针对伸展和无结构主体中氨基酸侧链的双层膜-水和辛醇-水分配所确定的ΔΔGtr值的约三分之二。α-螺旋主体背景下ΔΔGtr值的相对降低以及ΔΔGtr值相对于双层膜深度的不变性都与脂肪族残基的膜亲和力在很大程度上由经典疏水效应决定这一观点一致。
