醣胺素是具結構和功能多樣性的寡糖分子；這些分子已被証明和許多生物反應有關，例如細胞附著、移動、及經由與不同蛋白作用(如蛋白酶、細胞激素、生長激素、黏著分子等)的細胞分化現象。醣胺素分成六種，包括：硫酸乙醯肝素(HS)、肝素、硫酸軟骨素(CS)、硫酸皮膚素(DS)、硫酸角質素(KS)、透明質酸(HA)；在所有醣胺素裡，肝素是最被充分研究的，並且在1935年開始用作臨床抗凝血劑。最近的研究開始著重於肝素在生理上的重要功能，如在肥大細胞中肝素對特定顆粒酶之儲存的必要性等。對於肝素和帶正電蛋白間的作用除了電性交互作用外並不清楚。愈來愈多肝素結合蛋白被定性後，一般認為蛋白上與肝素的結合位也會受遠處連續胺基酸殘基影響而形成較好的結合表面。然而，包括之前研究提出的肝素結合關鍵保留序列，XBBXBX和XBBBXXBX，並沒有文獻能完整提供肝素-蛋白質的結合模式。因此我們利用以結構為導向的蛋白質轉接工程(protein grafting)來闡述蛋白質和肝素的結合位向。我們將一個熱穩定的蛋白模組，免疫球蛋白G結合蛋白G的B1模組，和肝素作用以獲得平面空間上的結合資訊。利用螢光輔助醣類電泳分析法(fluorophore-assisted carbohydrate electrophoresis analysis)，我們可以驗證B1模組四條折板構成的平面上正電胺基酸和肝素結合之數量和位向。結果顯示蛋白質二維空間上特定的間隔和胺基酸偏好(精氨酸)在與肝素結合的過程中扮演重要角色。

Glycosaminoglycans (GAGs) are polysaccharides with structural and functional diversity. These molecules have been demonstrated to be involved in a wide range of biological activities such as cell adhesion, cell mobility and cell proliferation through interacting with various cellular proteins, such as protease, cytokines, growth factors, adhesion molecules and so on. There are six classes of GAGs, including heparin sulfate (HS), heparin, chondroitin sulfate (CS), dermatan sulfate (DS), keratin sulfate (KS) and hyaluronic acid (HA); of all the GAG family members, heparin is the most well studied and has been used clinically as an anticoagulant since 1935. Recent experiments have shed light on the physiological significance of heparin which is essential for the storage of specific granule proteases in mast cells. The details of the interaction between heparin and positively charged proteins are not known except the electrostatic interactions seem to play an important role in this biomolecular association. With the characterization of more heparin-binding proteins, it was understood that the binding epitopes can also be defined by sequentially remote residues that form an optimal binding surface. However, none of these studies, such as the early studied key structural motifs of heparin-binding sequences XBBXBX and XBBBXXBX, have completely addressed the binding pattern for heparin-protein interactions. Therefore, we use a structure-guided approach, termed “protein grafting”, to elucidate the protein-heparin binding pattern. We targeted the heparin utilizing a thermal stable domain, B1 domain of IgG-binding protein G, and its derivatives because of its firmly packed conformation to accomplish spatial binding information. Through the planer four-beta-sheet scaffold design of B1 domain, the number and position of the positive amino acids within were verified by applying fluorophore-assisted carbohydrate electrophoresis analysis (FACE). The results reveal that the specific spacing and favored residue (arginine) seemed to be critical for heparin binding process.

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