NMR STRUCTURES OF PLATELET FACTOR 4 & B-THROMBOGLOBULIN

血小板因子（PF 4）和B-血小板球蛋白相关蛋白（BTG）低， 分子量肝素结合蛋白通常被认为是 血小板特异性的并且参与血液凝固、伤口愈合、组织 修复和细胞增殖。 已知PF 4可与肝素强结合 从而抑制凝血酶-抗凝血酶III复合物的形成， 血管部位。 PF 4的其他生理活性包括刺激 成纤维细胞附着在基质上，刺激组胺释放 人嗜碱性粒细胞的趋化活性和血小板增强作用 聚合来 虽然BTG与PF 4有约50%的序列同源性，但其 抗肝素活性较低，具有明显的促有丝分裂作用 在某些细胞类型中的活性，并抑制肝素对 抗凝血酶IIIa对Xa因子的中和作用大于PF 4。虽然 PF 4和BTG的结构被认为是生物学的关键， 功能，很少有人知道他们的结构功能，关系， 关于它们的构象是如何相关的，或者关于任何特定的结构， 与肝素或糖胺聚糖相互作用所必需的结构域 将军 这个项目的直接目标是阐明解决方案的结构 PF 4和低亲和力的Pf 4（LA-PF 4，其亲本蛋白质中， 通常称为BTG），并且长期目标是鉴定蛋白质- 肝素结合结构域。 PF 4和BTG结构的比较将给出 对后一点的初步认识。 使用的主要技术 实现这些目标的方法是高分辨率的二维质子核磁共振 光谱学与计算机建模研究相结合。 使用COSY- 类似和NOESY NMR实验，序列特异性质子共振 将在低pH值条件下对PF 4和BTG进行分配， 这些蛋白质以单体形式存在（7，800道尔顿）。 NOESY实验将 然后用于在比pH低的pH下建立距离四聚体结构， 更多的生理条件将通过NMR方法进行研究， 介绍了 四个紧密的联系，四面体相关，相同 单体使得通过NMR对32 kD四聚体进行结构解析变得可行 方法.

Platelet factor (PF4) and B-thromboglobulin-related proteins (BTG) are low- molecular weight heparin binding proteins generally considered to be platelet specific and are involved in blood clotting, wound healing, tissue repair and cell proliferation. PF4 is known to strongly bind heparin thereby inhibiting the formation of thrombin-antithrombin III complexes at vascular sites. Other physiological activities of PF4 include stimulation of fibroblast attachment to the substrate, stimulation of histamine release from human basophils, chemotactic activity, and potentiation of platelet aggregation. While BTG is about 50% sequentially homologous to PF4, its anti-heparin activity is less, and it possesses significant mitogenic activity in certain cell types and inhibits the catalytic effect heparin on Factor Xa neutralization by anti-thrombin IIIa more than does PF4. Although the structures of PF4 and BTG are considered critical to biological function, little is known about their structure-function, relationships, about how their conformations are related, or about any specific structural domain(s) essential for interaction with heparin or glycosaminoglycans in general. The immediate goal of this project is to elucidate the solution structures of PF4 and low affinity-Pf4 (LA-PF4, the parent protein of the more commonly known BTG), and the long range goal is to identity the protein- heparin binding domain(s). Comparison of PF4 and BTG structures will give initial insight into this latter point. The primary technique to be used towards these goals is high-resolution, two-dimensional proton NMR spectroscopy in combination with computer modeling studies. By using COSY- like and NOESY NMR experiments, sequence-specific proton resonance assignments will be made for PF4 and BTG at low ph under conditions where these proteins exist as monomers (7,800 daltons). NOESY experiments will then be used to establish distance tetrameric structures at low ph than at more physiological conditions will be investigated by NMR methods just described. The tight association of four, tetrahedral-related, identical monomers makes structural elucidation of the 32 kD tetramer feasible by NMR methods.