FRAGMENT OF LAMBDA REPRESSOR (L6 85) & DOUBLE MUTANT G46A & G48A L6 85

Lambda抑制物(16-85)是Lambda抑制物的可溶性片段。 含有残基6到85，保持天然的折叠 主要由阿尔法螺旋组成。差示扫描 WT(16-85)和双突变体G46A/G48A的量热分析 揭示突变的作用是通过以下方式稳定蛋白质 在25℃时约1.5千卡/摩尔(即WT为2.9千卡/摩尔和4.4千卡/摩尔 适用于G46/48A)。突变后稳定性的提高表明 突变对稳定性的主要影响是减少了 甘氨酸处于未折叠状态时的构象熵 取而代之的是Ala。然而，由于将甘氨酸改为 螺旋中两个位置的ALA为~2.4千卡/摩尔，~0.9千卡/摩尔 实验值和计算值之间的差异表明 就会产生额外的影响 从降低自然状态稳定性的突变中 双变异体的。

Lambda repressor (l6-85) is a soluble fragment of lambda repressor containing residues 6 to 85 which maintains a native-like fold consisting largely of alpha helices. Differential scanning calorimetry (DSC) of the WT (l6-85) and the double mutant G46A/G48A reveal that the effect of the mutations is to stabilize the protein by ~ 1.5 kcal/mol at 25 C (I.e., 2.9 kcal/mol for the WT and 4.4 kcal/mol for G46/48A). The increase in stability upon mutation suggests that the primary effect of the mutation on stability is the decrease in conformational entropy ( Sconf) of the unfolded state when Gly is replaced by Ala. However, as the calculated effect of changing Gly to Ala at two positions in a helix is ~ 2.4 kcal/mol, the ~0.9 kcal/mol difference between the experimental and calculated values suggests that additional effects arise from the mutations which decrease the stability of the native state of the double mutant.