University of Gdansk, Department of Medicinal Chemistry, Gdansk, Poland.
J Mol Recognit. 2013 Sep;26(9):415-25. doi: 10.1002/jmr.2283.
Secondary amyloid A (AA) amyloidosis is an important complication of some chronic inflammatory diseases, primarily rheumatoid arthritis (RA). It is a serious, potentially life-threatening disorder caused by the deposition of AA fibrils, which are derived from the circulatory, acute-phase-reactant, serum amyloid A protein (SAA). Recently, a specific interaction between SAA and the ubiquitous inhibitor of cysteine proteases--human cystatin C (hCC)--has been proved. Using a combination of selective proteolytic excision and high-resolution mass spectrometry, the binding sites in the SAA and hCC sequences were assessed as SAA(86-104) and hCC(96-102), respectively. Here, we report further details concerning the hCC-SAA interaction. With the use of affinity tests and florescent ELISA-like assays, the amino acid residues crucial for the protein interaction were determined. It was shown that all amino acid residues in the SAA sequence, essential for the formation of the protein complex, are basic ones, which suggests an electrostatic interaction character. The idea is corroborated by the fact that the most important residues in the hCC sequence are Ser-98 and Tyr-102; these residues are able to form hydrogen bonds via their hydroxyl groups. The molecular details of hCC-SAA complex formation might be helpful for the design of new compounds modulating the biological role of both proteins.
继发性淀粉样蛋白 A (AA) 淀粉样变性是一些慢性炎症性疾病的重要并发症，主要是类风湿关节炎 (RA)。它是一种严重的、潜在危及生命的疾病，由 AA 纤维的沉积引起，AA 纤维来源于循环、急性期反应物、血清淀粉样蛋白 A 蛋白 (SAA)。最近，已经证明了 SAA 与普遍存在的半胱氨酸蛋白酶抑制剂——人胱抑素 C (hCC) 之间的特定相互作用。使用选择性蛋白内切和高分辨率质谱组合，评估了 SAA 和 hCC 序列中的结合位点，分别为 SAA(86-104)和 hCC(96-102)。在这里，我们报告了有关 hCC-SAA 相互作用的进一步细节。通过使用亲和测试和荧光 ELISA 样测定，确定了对蛋白质相互作用至关重要的氨基酸残基。结果表明，形成蛋白质复合物所必需的 SAA 序列中的所有氨基酸残基都是碱性的，这表明存在静电相互作用特征。这一观点得到了 hCC 序列中最重要的残基是 Ser-98 和 Tyr-102 的事实的证实；这些残基能够通过其羟基形成氢键。hCC-SAA 复合物形成的分子细节可能有助于设计调节两种蛋白质生物作用的新化合物。
