Department of Chemistry, Trinity University, 1 Trinity Place, San Antonio, Texas 78212, USA.
J Am Chem Soc. 2011 Oct 26;133(42):17087-92. doi: 10.1021/ja207825y. Epub 2011 Oct 3.
This paper describes the molecular recognition of phenylalanine derivatives and their peptides by the synthetic receptor cucurbit[7]uril (Q7). The 4-tert-butyl and 4-aminomethyl derivatives of phenylalanine (tBuPhe and AMPhe) were identified from a screen to have 20-30-fold higher affinity than phenylalanine for Q7. Placement of these residues at the N-terminus of model tripeptides (X-Gly-Gly), resulted in no change in affinity for tBuPhe-Gly-Gly, but a remarkable 500-fold increase in affinity for AMPhe-Gly-Gly, which bound to Q7 with an equilibrium dissociation constant (K(d)) value of 0.95 nM in neutral phosphate buffer. Structure-activity studies revealed that three functional groups work in a positively cooperative manner to achieve this extraordinary stability (1) the N-terminal ammonium group, (2) the side chain ammonium group, and (3) the peptide backbone. Addition of the aminomethyl group to Phe substantially improved the selectivity for peptide versus amino acid and for an N-terminal vs nonterminal position. Importantly, Q7 binds to N-terminal AMPhe several orders of magnitude more tightly than any of the canonical amino acid residues. The high affinity, single-site selectivity, and small modification in this system make it attractive for the development of minimal affinity tags.
本文描述了苯丙氨酸衍生物及其肽与合成受体葫芦[7]脲（Q7）的分子识别。从筛选中鉴定出苯丙氨酸的 4-叔丁基和 4-甲氨基衍生物（tBuPhe 和 AMPhe），与 Q7 相比，它们对 Q7 的亲和力高 20-30 倍。将这些残基置于模型三肽（X-Gly-Gly）的 N 末端，tBuPhe-Gly-Gly 的亲和力没有变化，但 AMPhe-Gly-Gly 的亲和力显著增加了 500 倍，与 Q7 的平衡解离常数（K(d)）值为 0.95 nM 在中性磷酸盐缓冲液中。结构活性研究表明，三个功能基团以正协同方式协同作用，实现了这种非凡的稳定性：（1）N 末端铵基团，（2）侧链铵基团，和（3）肽骨架。在苯丙氨酸中加入甲氨基基团可大大提高肽与氨基酸的选择性，以及 N 末端与非末端位置的选择性。重要的是，Q7 与 N 末端 AMPhe 的结合亲和力比任何经典氨基酸残基都高几个数量级。该体系具有高亲和力、单一位点选择性和微小修饰，使其成为开发最小亲和力标签的有吸引力的选择。
