Sayed Y, Wallace L A, Dirr H W
Protein Structure-Function Research Programme, Department of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, South Africa.
FEBS Lett. 2000 Jan 14;465(2-3):169-72. doi: 10.1016/s0014-5793(99)01747-0.
A hydrophobic lock-and-key intersubunit motif involving a phenylalanine is a major structural feature conserved at the dimer interface of classes alpha, mu and pi glutathione transferases. In order to determine the contribution of this subunit interaction towards the function and stability of human class alpha GSTA1-1, the interaction was truncated by replacing the phenylalanine 'key' Phe-51 with serine. The F51S mutant protein is dimeric with a native-like core structure indicating that Phe-51 is not essential for dimerization. The mutation impacts on catalytic and ligandin function suggesting that tertiary structural changes have occurred at/near the active and non-substrate ligand-binding sites. The active site appears to be disrupted mainly at the glutathione-binding region that is adjacent to the lock-and-key intersubunit motif. The F51S mutant displays enhanced exposure of hydrophobic surface and ligandin function. The lock-and-key motif stabilizes the quaternary structure of hGSTA1-1 at the dimer interface and the protein concentration dependence of stability indicates that the dissociation and unfolding processes of the mutant protein remain closely coupled.
涉及苯丙氨酸的疏水锁钥亚基间基序是α、μ和π类谷胱甘肽转移酶二聚体界面保守的主要结构特征。为了确定这种亚基相互作用对人α类GSTA1-1功能和稳定性的贡献，通过将苯丙氨酸“钥匙”Phe-51替换为丝氨酸来截断这种相互作用。F51S突变蛋白是具有天然样核心结构的二聚体，表明Phe-51对二聚化不是必需的。该突变影响催化和配体结合功能，表明在活性和非底物配体结合位点处/附近发生了三级结构变化。活性位点似乎主要在与锁钥亚基间基序相邻的谷胱甘肽结合区域被破坏。F51S突变体表现出疏水表面和配体结合功能的暴露增强。锁钥基序在二聚体界面稳定hGSTA1-1的四级结构，并且稳定性的蛋白质浓度依赖性表明突变蛋白的解离和去折叠过程仍然紧密耦合。
