Studies on the molecular mechanism of thrombin receptor activation by means of ligand peptides containing a series of fluorinated phenylalanines

丝氨酸蛋白酶凝血酶受体是一种新型的受体，其中的多肽配体存在于受体本身的N端部分。研究发现，合成肽Ser-Phe-Leu-Leu-Arg-Asn-Pro(SFLLRNP)可以在没有凝血酶的情况下激活该受体，并且该肽的Phe-2对该受体至关重要。识别和激活。本研究的目的是阐明Phe-2-苯基与凝血酶受体芳香族基团的相互作用模式。配体Phe-苯基的相互作用有两种可能：即pi-pi堆积相互作用和CH/pi相互作用。为了区分这些相互作用，我们加入了一系列氟化苯丙氨酸。氟是电负性最强的原子，其大小几乎与氢相同。人们立即认识到，只允许在对位上进行氟取代。含五氟苯丙氨酸的衍生物完全不含…更多的活动。这些结果表明，Phe-2可能需要苯环上的氢原子(S)与受体相互作用。对氯丙氨酸、溴丙氨酸或碘苯丙氨酸的类似物没有观察到活性增强，这表明氟的高电负性对于加强保留在Phe-2-苯丙氨酸中的CH(S)的偶极是重要的，并表明存在面对面的pi-pi相互作用。被3，4，5-三氟苯丙氨酸的衍生物还原但完全激活，在第6位标记了一个氢，作为与受体芳香环直接相互作用的结构元素。当引入强间位取向的三氟甲基时，只有3-三氟甲基苯丙氨酸的衍生物具有完全的活性。所有这些结果表明，5和6位的氢是受体相互作用的最重要的结构元素，SFLLRNP的Phe-2相互作用似乎是基于Phe-2-苯基和受体芳香基之间的CH/pi相互作用的面到边的pi-pi相互作用。较少

The receptor of serine protease thrombin is a novel type of receptor, in which the peptite ligand is present in the N-terminal portion of the receptor itself. It was found that the receptor can be activated by the synthetic peptide Ser-Phe-Leu-Leu-Arg-Asn-Pro (SFLLRNP) without thrombin, and that Phe-2 of this peptide is crucially important to the receptor. recognition and activation. The aim of the present study is to clarify the interaction mode between Phe-2-phenyl and thrombin receptor aromatic groups. There are two possibilities for interaction of the ligand Phe-phenyl group : i.e., pi-pi stacking interaction and CH/pi interaction. To differentiate these interactions, we have incorporated a series of fluorinated phenylalanines. Fluorine is the most electronegative atom, the size of which is almost the same as hydrogen. It was immediately recognized that the fluorine substitution is allowed ony at the para-position. The derivative with pentafluorophenylalanine was totally devoid of … More activity. These results suggested that Phe-2 requires hydrogen atom(s) on the benzene ring presumably for interaction with the receptor. No activity enhancement observed for analogs with para-chloro-, bromo-, or iodophenylalanine indicated the importance of a high electronegativity of fluorine to intensify a dipole of CH(s) remaining in the Phe-2-benzenering, and suggested the presence of face-to-edge pi-pi interaction. Reduced but full activation by the derivative of 3,4,5-trifluorophenylalanine marked a hydrogen at position 6 as a structural element for direct interaction with the receptor aromatic ring. When strongly meta-orienting the trifluoromethyl group was introduced, only the derivative of 3-trifluoromethylpehnylalanine was fully active. All these results indicated that hydrogens at position 5 and 6 are the most important structural element for receptor interaction and that the interaction of Phe-2 of SFLLRNP appeared to be a face-to-edge pi-pi interaction based upon the CH/pi interaction between the Phe-2-phenyl group and the receptor aromatic group. Less