Fromm J R, Hileman R E, Weiler J M, Linhardt R J
Division of Medicinal and Natural Products Chemistry, University of Iowa, Iowa City 52242, USA.
Arch Biochem Biophys. 1997 Oct 15;346(2):252-62. doi: 10.1006/abbi.1997.0299.
Fibroblast growth factors (FGFs) are a family of angiogenic and mitogenic proteins that promote cell division. The binding of FGFs to the heparan sulfate of cell-surface-bound proteoglycans appears to be critical for their activity. The interaction of fibroblast growth factor-1 (FGF-1 or aFGF) using heparin lyase-derived oligosaccharides from heparan sulfate was investigated. FGF-1 was also shown to protect sequences in heparan sulfate from heparin lyase digestion and protected oligosaccharide products of octasaccharide and decasaccharide size were recovered by FGF-1 affinity chromatography, suggesting that the high-affinity binding of heparan sulfate to FGF-1 resides within an octasaccharide sequence. The FGF-1 binding affinity of heparan sulfate is reduced compared to heparin presumably due to the absence of 6-sulfate groups in heparan sulfate. Inspection of the FGF-1 heparan sulfate binding domain shows that the majority of interacting amino acids are contained within a 20-amino-acid sequence that folds back upon itself (because of three turns) forming a triangular shaped cup of positive charge. The importance of FGF-1 binding site topology was investigated using three synthetic peptide mimics of the FGF-1 glycosaminoglycan (GAG) binding site. Heparan sulfate affinity chromatography and isothermal titration calorimetry, used to measure binding thermodynamics, demonstrated that a synthetic peptide analogous to the GAG binding site in FGF-1 bound tightly to heparan sulfate. A peptide containing a D-proline in place of L-proline bound with considerably reduced affinity, presumably due to the altered structure of the second turn in the binding site. A cyclic peptide, expected to be topologically most similar to the triangular GAG binding site in FGF-1, bound with the highest affinity to heparan sulfate. These data suggest the triangular topology of the GAG binding site in FGF is critical for its interaction with heparan sulfate. Analysis of known GAG binding sites in 25 proteins using the Chou-Fasman algorithm show that these sites commonly contain turns.
成纤维细胞生长因子（FGFs）是一类促血管生成和有丝分裂的蛋白质家族，可促进细胞分裂。FGFs与细胞表面结合蛋白聚糖的硫酸乙酰肝素结合似乎对其活性至关重要。研究了成纤维细胞生长因子-1（FGF-1或酸性FGF）与硫酸乙酰肝素中肝素酶衍生的寡糖的相互作用。FGF-1还显示可保护硫酸乙酰肝素中的序列不被肝素酶消化，并且通过FGF-1亲和层析回收了八糖和十糖大小的寡糖产物，这表明硫酸乙酰肝素与FGF-1的高亲和力结合存在于八糖序列中。与肝素相比，硫酸乙酰肝素对FGF-1的结合亲和力降低，这可能是由于硫酸乙酰肝素中不存在6-硫酸基团。对FGF-1硫酸乙酰肝素结合域的检查表明，大多数相互作用的氨基酸包含在一个20个氨基酸的序列中，该序列自身折叠（由于三个转折）形成一个带正电荷的三角形杯状结构。使用FGF-1糖胺聚糖（GAG）结合位点的三种合成肽模拟物研究了FGF-1结合位点拓扑结构的重要性。用于测量结合热力学的硫酸乙酰肝素亲和层析和等温滴定量热法表明，一种类似于FGF-1中GAG结合位点的合成肽与硫酸乙酰肝素紧密结合。一种含有D-脯氨酸代替L-脯氨酸的肽结合亲和力大大降低，这可能是由于结合位点中第二个转折的结构改变所致。一种环状肽，预计在拓扑结构上与FGF-1中的三角形GAG结合位点最相似，与硫酸乙酰肝素的结合亲和力最高。这些数据表明FGF中GAG结合位点的三角形拓扑结构对其与硫酸乙酰肝素的相互作用至关重要。使用Chou-Fasman算法分析25种蛋白质中已知的GAG结合位点表明，这些位点通常包含转折结构。
