Hydrophobic effect and hydrogen bonds account for the improved activity of a complement inhibitor, compstatin
Hydrophobic effect and hydrogen bonds account for the improved activity of a complement inhibitor, compstatin
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DOI：
10.1021/jm0603419
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发表时间：
2006-07-27
影响因子：
7.3
通讯作者：
Lambris, John D.
中科院分区：
文献类型：
--
作者：
Katragadda, Madan;Magotti, Paola;Lambris, John D.
补体抑制剂坎普他汀（compstatin）第4位和第7位的色氨酸对其与C3的相互作用至关重要。然而，迄今为止，它们参与的性质尚未得到研究。在此，我们通过在这两个位置引入各种色氨酸类似物（5 - 甲基色氨酸、5 - 氟色氨酸、1 - 甲基色氨酸和2 - 萘丙氨酸），并通过酶联免疫吸附测定（ELISA）评估所得肽的活性以及通过等温滴定量热法（ITC）评估其结合能力，来研究由芳香族残基介导的C3 - 坎普他汀相互作用中所涉及的分子力。在所有坎普他汀类似物中，在第4位含有1 - 甲基色氨酸的肽表现出最高的结合亲和力（Kd = 15 nM）和活性（IC50 = 0.205 μM），其次是在第7位含有5 - 氟色氨酸的肽。我们的观察结果表明，涉及第4位残基的疏水相互作用以及由吲哚氮引发的氢键是活性增加的主要原因且至关重要。这些发现对临床上有用的补体抑制剂的设计具有重要意义。
Tryptophans at positions 4 and 7 of compstatin, a peptide complement inhibitor, are crucial for its interaction with C3. However, the nature of their involvement has not been studied to date. Here we investigate the molecular forces involved in the C3- compstatin interactions, mediated by aromatic residues, by incorporating in these two positions various tryptophan analogues (5-methyltryptophan, 5-fluorotryptophan, 1-methyltryptophan, and 2-naphthylalanine) and assessing the resulting peptides for activity by enzyme-linked immunosorbent assay (ELISA) and binding by isothermal titration calorimetry (ITC). Of all the compstatin analogues, peptides containing 1-methyltryptophan at position 4 exhibited the highest binding affinity (K-d = 15 nM) and activity (IC50 = 0.205 mu M), followed by a peptide containing 5-fluorotryptophan at position 7. Our observations suggest that hydrophobic interactions involving residues at position 4 and the hydrogen bond initiated by the indole nitrogen are primarily responsible and crucial for the increase in activity. These findings have important implications for the design of clinically useful complement inhibitors.