McClintock Kimberly A, Shaw Gary S
Department of Biochemistry and McLaughlin Macromolecular Structure Facility, the University of Western Ontario, London, Ontario N6A 5C1, Canada.
J Biol Chem. 2003 Feb 21;278(8):6251-7. doi: 10.1074/jbc.M210622200. Epub 2002 Dec 11.
The Alzheimer-linked neural protein S100B is a signaling molecule shown to control the assembly of intermediate filament proteins in a calcium-sensitive manner. Upon binding calcium, a conformational change occurs in S100B exposing a hydrophobic surface for target protein interactions. The synthetic peptide TRTK-12 (TRTKIDWNKILS), derived from random bacteriophage library screening, bears sequence similarity to several intermediate filament proteins and has the highest calcium-dependent affinity of any target molecule for S100B to date (K(d) <1 microm). In this work, the three-dimensional structure of the Ca(2+)-S100B-TRTK-12 complex has been determined by NMR spectroscopy. The structure reveals an extended, contiguous hydrophobic surface is formed on Ca(2+)-S100B for target interaction. The TRTK-12 peptide adopts a coiled structure that fits into a portion of this surface, anchored at Trp(7), and interacts with multiple hydrophobic contacts in helices III and IV of Ca(2+)-S100B. This interaction is strikingly different from the alpha-helical structures found for other S100 target peptides. By using the TRTK-12 interaction as a guide, in combination with other available S100 target structures, a recognition site on helix I is identified that may act in concert with the TRTK-12-binding site from helices III and IV. This would provide a larger, more complex site to interact with full-length target proteins and would account for the promiscuity observed for S100B target protein interactions.
与阿尔茨海默病相关的神经蛋白S100B是一种信号分子，已被证明能以钙敏感的方式控制中间丝蛋白的组装。与钙结合后，S100B会发生构象变化，暴露出一个疏水表面用于与靶蛋白相互作用。从随机噬菌体文库筛选中获得的合成肽TRTK-12（TRTKIDWNKILS）与几种中间丝蛋白具有序列相似性，并且是迄今为止对S100B具有最高钙依赖性亲和力的任何靶分子（解离常数K(d)<1微摩尔）。在这项工作中，通过核磁共振光谱法确定了Ca(2+)-S100B-TRTK-12复合物的三维结构。该结构揭示了在Ca(2+)-S100B上形成了一个延伸的、连续的疏水表面用于靶标相互作用。TRTK-12肽采用一种卷曲结构，该结构适合该表面的一部分，锚定在色氨酸(7)处，并与Ca(2+)-S100B的螺旋III和IV中的多个疏水接触相互作用。这种相互作用与其他S100靶肽的α-螺旋结构明显不同。以TRTK-12的相互作用为指导，结合其他可用的S100靶标结构，在螺旋I上确定了一个识别位点，该位点可能与来自螺旋III和IV的TRTK-12结合位点协同作用。这将提供一个更大、更复杂的位点来与全长靶蛋白相互作用，并可以解释观察到的S100B靶蛋白相互作用的混杂性。
