Umemoto K, Oikawa S, Aida M, Sugawara Y
Department of Chemistry, International Christian University, Mitaka, Tokyo, Japan.
J Biomol Struct Dyn. 1988 Dec;6(3):593-608. doi: 10.1080/07391102.1988.10506510.
The detailed binding mechanism of wheat germ agglutinin (WGA) with N-acetylglucosamine (GlcNAc) was investigated using intermolecular 1H-1H nuclear Overhauser effect (NOE) and atomic pair potential (APP) calculations. Negative NOE was observed on the 1H spectrum of 1-O-methyl derivative of GlcNAc in a solution containing WGA, when the aromatic region of the WGA spectrum was irradiated. Analyses of the time dependence of NOE revealed that H2 and the N-acetyl methyl protons of the sugar are in close proximity to the aromatic protons of WGA in the bound state. This was confirmed and further elucidated by the APP calculations. According to the calculation, the major binding force comes from a hydrogen-bonding between C3-OH of sugar and an acidic residue present in each of the two binding sites of WGA: Glu115 in site 1 and Asp29 in site 2. The binding is further assisted by the N-acetyl group which interacts with a few more polar amino acid residues in the binding sites. The optimized binding mode suggested by the APP calculations supports the NMR results in that H2 and a part of the N-acetyl methyl protons are within 4.5 A distance from protons of both Tyr64 and Tyr73 in site 1 and of Tyr159 in site 2.
利用分子间1H-1H核Overhauser效应（NOE）和原子对势（APP）计算，研究了麦胚凝集素（WGA）与N-乙酰葡糖胺（GlcNAc）的详细结合机制。当照射WGA光谱的芳香区时，在含有WGA的溶液中，GlcNAc的1-O-甲基衍生物的1H光谱上观察到负NOE。对NOE时间依赖性的分析表明，在结合状态下，糖的H2和N-乙酰基质子与WGA的芳香质子非常接近。这一点通过APP计算得到了证实并进一步阐明。根据计算，主要结合力来自糖的C3-OH与WGA两个结合位点中每个位点存在的酸性残基之间的氢键：位点1中的Glu115和位点2中的Asp29。N-乙酰基与结合位点中的一些更多极性氨基酸残基相互作用，进一步促进了结合。APP计算提出的优化结合模式支持了NMR结果，即H2和部分N-乙酰基质子与位点1中的Tyr64和Tyr73以及位点2中的Tyr159的质子距离在4.5埃以内。
