CNR Istituto di Cristallografia Sede Secondaria di Catania, Via Gaifami 18, 95126 Catania, Italy.
Dipartimento di Farmacia, Università di Pisa, Via Bonanno Pisano 6, 56126 Pisa, Italy.
Int J Mol Sci. 2020 Dec 8;21(24):9343. doi: 10.3390/ijms21249343.
The antiangiogenic activity of the H/P domain of histidine-proline-rich glycoprotein is mediated by its binding with tropomyosin, a protein exposed on endothelial cell-surface during the angiogenic switch, in presence of zinc ions. Although it is known that copper ion serum concentration is significantly increased in cancer patients, its role in the interaction of H/P domain with tropomyosin, has not yet been studied. In this paper, by using ELISA assay, we determined the modulating effect of TetraHPRG peptide, a sequence of 20 aa belonging to H/P domain, on the binding of Kininogen (HKa) with tropomyosin, both in absence and presence of copper and zinc ions. A potentiometric study was carried out to characterize the binding mode adopted by metal ions with TetraHPRG, showing the formation of complex species involving imidazole amide nitrogen atoms in metal binding. Moreover, circular dichroism showed a conformational modification of ternary systems formed by TetraHPRG, HKa and copper or zinc. Interestingly, slight pH variation influenced the HKa-TetraHPRG-tropomyosin binding. All these results indicate that both metal ions are crucial in the interaction between TetraHPRG, tropomyosin and HKa.
富含组氨酸-脯氨酸的糖蛋白的 H/P 结构域的抗血管生成活性是通过其与微管蛋白结合介导的，微管蛋白是血管生成开关期间内皮细胞表面暴露的一种蛋白，存在锌离子。虽然已知癌症患者血清中铜离子浓度显著增加，但铜离子在 H/P 结构域与微管蛋白相互作用中的作用尚未得到研究。在本文中，我们通过 ELISA 测定法，确定了 TetraHPRG 肽（属于 H/P 结构域的 20 个氨基酸序列）对激肽原（HKa）与微管蛋白结合的调节作用，包括在缺乏和存在铜和锌离子的情况下。进行了电位测定研究以表征金属离子与 TetraHPRG 的结合方式，表明形成了涉及金属结合中咪唑酰胺氮原子的配合物物种。此外，圆二色性显示了由 TetraHPRG、HKa 和铜或锌形成的三元体系的构象修饰。有趣的是，稍微的 pH 值变化会影响 HKa-TetraHPRG-微管蛋白的结合。所有这些结果表明，两种金属离子在 TetraHPRG、微管蛋白和 HKa 之间的相互作用中都是至关重要的。
