Department of Chemistry, College of Staten Island , City University of New York , 2800 Victory Boulevard , Staten Island , New York 10314 , United States.
Ph.D. Programs in Biochemistry and Chemistry , The Graduate Center of the City University of New York , New York , New York 10016 , United States.
Biochemistry. 2019 Apr 30;58(17):2269-2281. doi: 10.1021/acs.biochem.9b00123. Epub 2019 Apr 18.
S100A12 is a member of the Ca binding S100 family of proteins that functions within the human innate immune system. Zinc sequestration by S100A12 confers antimicrobial activity when the protein is secreted by neutrophils. Here, we demonstrate that Ca binding to S100A12's EF-hand motifs and Zn binding to its dimeric interface cooperate to induce reversible self-assembly of the protein. Solution and magic angle spinning nuclear magnetic resonance spectroscopy on apo-, Ca-, Zn-, and Ca,Zn-S100A12 shows that significant metal binding-induced chemical shift perturbations, indicative of conformational changes, occur throughout the polypeptide chain. These perturbations do not originate from changes in the secondary structure of the protein, which remains largely preserved. While the overall structure of S100A12 is dominated by Ca binding, Zn binding to Ca-S100A12 introduces additional structural changes to helix II and the hinge domain (residues 38-53). The hinge domain of S100A12 is involved in the molecular interactions that promote chemotaxis for human monocyte, acute inflammatory responses and generates edema. In Ca-S100A12, helix II and the hinge domain participate in binding with the C-type immunoglobulin domain of the receptor for advanced glycation products (RAGE). We discuss how the additional conformational changes introduced to these domains upon Zn binding may also impact the interaction of S100A12 and target proteins such as RAGE.
S100A12 是 S100 家族成员之一，属于钙结合蛋白，在人类先天免疫系统中发挥作用。当 S100A12 由中性粒细胞分泌时，其通过螯合锌来发挥抗菌作用。在这里，我们证明 S100A12 的 EF 手模体与 Ca 结合以及其二聚体界面与 Zn 结合可共同诱导蛋白的可逆自组装。无金属结合物、Ca 结合物、Zn 结合物和 Ca、Zn 结合物的 S100A12 的溶液和魔角旋转核磁共振波谱显示，整个多肽链都发生了显著的金属结合诱导的化学位移扰动，表明构象发生了变化。这些扰动并非源于蛋白质二级结构的改变，该结构基本保持不变。虽然 S100A12 的整体结构主要由 Ca 结合决定，但 Zn 与 Ca-S100A12 的结合会引起螺旋 II 和铰链域（残基 38-53）的结构变化。S100A12 的铰链域参与了促进人单核细胞趋化、急性炎症反应和生成水肿的分子相互作用。在 Ca-S100A12 中，螺旋 II 和铰链域参与与晚期糖基化产物受体（RAGE）的 C 型免疫球蛋白域的结合。我们讨论了在这些结构域中引入 Zn 结合后引入的额外构象变化如何也可能影响 S100A12 与 RAGE 等靶蛋白的相互作用。
