Lab of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao 266101, China.
J Mol Model. 2012 Apr;18(4):1355-64. doi: 10.1007/s00894-011-1167-4. Epub 2011 Jul 15.
A critical role of the Family 7 cellobiohydrolase (Cel7A) carbohydrate binding domain (CBD) is to bind to a cellulose surface and increase the enzyme concentration on the surface. Several residues of Trichoderma reesei Cel7A CBD, including Y5, N29, Y31, Y32 and Q34, contribute to cellulose binding, as revealed by early experimental studies. To investigate the interactions between these important residues and cellulose, we applied a thermodynamic integration method to calculate the cellulose-Cel7A CBD binding free energy changes caused by Y5A, N29A, Y31A, Y32A and Q34A mutations. The experimental binding trend was successfully predicted, proving the effectiveness of the complex model. For the two polar residue mutants N29A and Q34A, the changes in the electrostatics are comparable to those of van der Waals, while for three Y to A mutants, the free energy differences mainly come from van der Waals interactions. However, in both cases, the electrostatics dominates the interactions between individual residues and cellulose. The side chains of these residues are rigidified after the complex is formed. The binding free energy changes for the two mutants Y5W and Y31W were also determined, and for these the van der Waals interaction was strengthened but the electrostatics was weakened.
纤维二糖水解酶家族 7（Cel7A）碳水化合物结合结构域（CBD）的一个关键作用是与纤维素表面结合，并增加表面的酶浓度。木霉 Cel7A CBD 的几个残基，包括 Y5、N29、Y31、Y32 和 Q34，有助于纤维素结合，这一点在早期的实验研究中已经得到证实。为了研究这些重要残基与纤维素之间的相互作用，我们应用热力学积分方法计算了 Y5A、N29A、Y31A、Y32A 和 Q34A 突变引起的纤维素-Cel7A CBD 结合自由能变化。实验结合趋势得到了成功预测，证明了复杂模型的有效性。对于两个极性残基突变体 N29A 和 Q34A，静电变化与范德华力相当，而对于三个 Y 到 A 的突变体，自由能差异主要来自范德华相互作用。然而，在这两种情况下，静电都主导着单个残基与纤维素之间的相互作用。在形成复合物后，这些残基的侧链变得僵硬。还确定了两个突变体 Y5W 和 Y31W 的结合自由能变化，对于这两个突变体，范德华相互作用得到了加强，但静电相互作用减弱了。
