Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan.
J Am Chem Soc. 2013 Aug 21;135(33):12297-304. doi: 10.1021/ja405044k. Epub 2013 Aug 8.
Cyclic structures can increase the proteolytic stability and conformational rigidity of peptides, and N-alkylation of the peptide backbone can make peptides more cell-permeable and resistant to proteolysis. Therefore, cyclic N-alkyl amino acids are expected to be useful building blocks to increase simultaneously these pharmacological properties of peptides. In this study, we screened various cyclic N-alkyl amino acids for their ribosomal incorporation into peptides and identified cyclic N-alkyl amino acids that can be efficiently and successively incorporated. We also demonstrated genetic code reprogramming for reassigning 16 NNU codons to 16 different cyclic N-alkyl amino acids with high fidelity to synthesize highly N-alkylated polycyclic peptidomimetics and an mRNA-displayed library of completely N-alkylated polycyclic peptidomimetics by using our recently developed TRAP (transcription/translation coupled with association of puromycin linker) display. In vitro selection from a highly diverse library of such completely N-alkylated polycyclic peptidomimetics could become a powerful means to discover small-molecule ligands such as drug candidates that can be targeted to biomolecules inside living cells.
环状结构可以提高肽的蛋白水解稳定性和构象刚性，并且肽主链的 N-烷基化可以使肽具有更好的细胞通透性和抗蛋白水解能力。因此，环状 N-烷基氨基酸有望成为增加肽类这些药理学性质的有用构建块。在这项研究中，我们筛选了各种环状 N-烷基氨基酸，以研究它们在肽中的核糖体掺入情况，并确定了可以有效且连续掺入的环状 N-烷基氨基酸。我们还通过使用我们最近开发的 TRAP（转录/翻译偶联与嘌呤霉素连接物的缔合）展示，展示了遗传密码重编程，将 16 个 NNU 密码子重新分配给 16 种不同的环状 N-烷基氨基酸，以高保真度合成高度 N-烷基化的多环肽模拟物和完全 N-烷基化的多环肽模拟物的 mRNA 展示文库。从如此高度多样化的完全 N-烷基化多环肽模拟文库中进行体外选择可能成为发现小分子配体（如药物候选物）的有效手段，这些小分子配体可以靶向活细胞内的生物分子。
