Fairman R, Chao H G, Lavoie T B, Villafranca J J, Matsueda G R, Novotny J
Division of Macromolecular Structure, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey 08543-4000, USA.
Biochemistry. 1996 Mar 5;35(9):2824-9. doi: 10.1021/bi952784c.
Electrostatic interactions between charged amino acids often affect heterospecificity in coiled coils as evidenced by the interaction between the oncoproteins, fos and jun. Such interactions have been successfully exploited in the design of heteromeric coiled coils in a number of laboratories. It has been suggested that heterospecificity in these dimeric coiled-coil systems is driven not by specific electrostatic interactions in the heterodimers but rather by electrostatic repulsion acting to destabilize the homodimer state relative to the heterodimer state. We show that it is possible to design ion pair interactions that directly stabilize the heterotetrameric coiled-coil state. Synthetic peptides were used whose sequences are based on the C-terminal tetramerization domain of Lac repressor, as a model system for four-chain coiled coils (Fairman et al., 1995). These Lac-based peptides, containing either glutamic acid (Lac21E) or lysine (Lac21K) at all b and c heptad positions, only weakly self-associate but, when mixed, afford a highly stable heterotetramer. This study represents the first experimental evidence for the importance of the b and c heptad positions to the stability of coiled coils. Finally, pH dependence and NaCl dependence studies show that heterotetramer stability is driven by ion pair interactions between glutamate and lysine; these interactions contribute about 0.6 kcal/mol of stabilizing free energy for each potential glutamate-lysine pair.
带电氨基酸之间的静电相互作用常常影响卷曲螺旋中的异特异性，癌蛋白fos和jun之间的相互作用就证明了这一点。在许多实验室中，这种相互作用已成功用于异源卷曲螺旋的设计。有人提出，这些二聚体卷曲螺旋系统中的异特异性不是由异二聚体中的特定静电相互作用驱动的，而是由静电排斥作用驱动的，这种排斥作用使同二聚体状态相对于异二聚体状态不稳定。我们表明，可以设计直接稳定异源四聚体卷曲螺旋状态的离子对相互作用。使用了合成肽，其序列基于乳糖阻遏物的C末端四聚化结构域，作为四链卷曲螺旋的模型系统（Fairman等人，1995年）。这些基于乳糖的肽在所有b和c七肽位置含有谷氨酸（Lac21E）或赖氨酸（Lac21K），仅弱自缔合，但混合时可形成高度稳定的异源四聚体。这项研究代表了b和c七肽位置对卷曲螺旋稳定性重要性的首个实验证据。最后，pH依赖性和NaCl依赖性研究表明，异源四聚体稳定性由谷氨酸和赖氨酸之间的离子对相互作用驱动；对于每个潜在的谷氨酸-赖氨酸对，这些相互作用贡献约0.6千卡/摩尔的稳定自由能。
