Trontskiĭ A V, Chirgadze Iu N, Brazhnikov E V
Biokhimiia. 1979 Oct;44(10):1864-76.
The structural changes of bacteriophage T4 lysozyme during its binding to the inhibitor, i. e. disaccharide-tetrapeptide N-acetylglucosaminyl-N-acetylmuraminyl - L - alanyl-gamma-D-glutaminyl - mesodiaminopimelyl-D-alanine) isolated from Escherichia coli cell wall have been studied. During the inhibitor binding to the protein the degree of helicity decreases by approximately 14% as was shown using the circular dichroism technique. The changes in optical properties of tryptophane, tyrosine and phenylalanine residues detected by UV difference and fluorescence spectroscopy have been observed. Based on the experimental data and a comparison of spatial organization of phage T4 lysozyme and chicken egg-white lysozyme made it possible to develop a structural model of phage T4 lysozyme functioning. This model may account for the differences in specificity of action of bacteriophage T4 and chicken egg-white lysozymes and allows to establish the role of the "extra" part of phage lysozyme. According to the model, at the first stage of binding the peptide part of the substrate comes in contact with the "upper" (with respect to the cleft) part of the protein molecule (residues 106--116 and 135--140). This results in rearrangement of the molecule, with opening of the cleft at the second stage. This makes possible the access of the polysaccharide part of the substrate of the active site and a subsequent hydrolysis of the beta (1 leads to 4) glycoside bond.
研究了噬菌体T4溶菌酶在与从大肠杆菌细胞壁分离出的抑制剂（即二糖 - 四肽N - 乙酰葡糖胺基 - N - 乙酰胞壁酰 - L - 丙氨酰 - γ - D - 谷氨酰胺基 - 内消旋二氨基庚二酸 - D - 丙氨酸）结合过程中的结构变化。如使用圆二色性技术所示，在抑制剂与蛋白质结合过程中，螺旋度降低了约14%。观察到通过紫外差光谱和荧光光谱检测到的色氨酸、酪氨酸和苯丙氨酸残基光学性质的变化。基于实验数据以及对噬菌体T4溶菌酶和鸡蛋白溶菌酶空间组织的比较，得以构建噬菌体T4溶菌酶功能的结构模型。该模型可以解释噬菌体T4溶菌酶和鸡蛋白溶菌酶作用特异性的差异，并有助于确定噬菌体溶菌酶“额外”部分的作用。根据该模型，在结合的第一阶段，底物的肽部分与蛋白质分子的“上部”（相对于裂隙）部分（残基106 - 116和135 - 140）接触。这导致分子重排，在第二阶段裂隙打开。这使得底物的多糖部分能够进入活性位点并随后水解β（1→4）糖苷键。
