Question

Macmillan Learning Temperature (°C) Suppose that a Met residue buried in the folded, hydrophobic core of T4 lysozyme is replaced by mutation with a Lys residue. How would the Met to Lys mutation affect the thermal denaturation of lysozyme at pH 3.0? ? It will not affect stability, but it will decrease the $T_m$ and shift the curve to lower temperatures. ? It will destabilize the protein and lower the $T_m$, shifting the curve to the left. ? It will stabilize the protein and raise the $T_m$, shifting the curve to higher temperatures. ? It will not change the $T_m$ at pH 3.0 because the Lys side chain $pK_a$ is 10.53. Suppose that the thermal denaturation experiment on the protein with the Met to Lys mutation took place at pH 10.0. Would the mutation have a greater or lesser impact on stability at pH 10.0 compared to pH 3.0? ? lesser, because a less acidic environment contributes to general protein stability ? lesser, because a greater fraction of Lys can remain buried in the core at pH 10.0 ? no change, because the Lys side chain $pK_a$ is above 10.0 so the side chain remains charged ? greater, because high pH values destabilize proteins

          Macmillan Learning
Temperature (°C)
Suppose that a Met residue buried in the folded, hydrophobic core of T4 lysozyme is replaced by mutation with a Lys residue.
How would the Met to Lys mutation affect the thermal denaturation of lysozyme at pH 3.0?
? It will not affect stability, but it will decrease the $T_m$ and shift the curve to lower temperatures.
? It will destabilize the protein and lower the $T_m$, shifting the curve to the left.
? It will stabilize the protein and raise the $T_m$, shifting the curve to higher temperatures.
? It will not change the $T_m$ at pH 3.0 because the Lys side chain $pK_a$ is 10.53.
Suppose that the thermal denaturation experiment on the protein with the Met to Lys mutation took place at pH 10.0.
Would the mutation have a greater or lesser impact on stability at pH 10.0 compared to pH 3.0?
? lesser, because a less acidic environment contributes to general protein stability
? lesser, because a greater fraction of Lys can remain buried in the core at pH 10.0
? no change, because the Lys side chain $pK_a$ is above 10.0 so the side chain remains charged
? greater, because high pH values destabilize proteins

$Macmillan Learning Temperature (°C) Suppose that a Met residue buried in the folded, hydrophobic core of T4 lysozyme is replaced by mutation with a Lys residue. How would the Met to Lys mutation affect the thermal denaturation of lysozyme at pH 3.0? ? It will not affect stability, but it will decrease the Tm and shift the curve to lower temperatures. ? It will destabilize the protein and lower the Tm, shifting the curve to the left. ? It will stabilize the protein and raise the Tm, shifting the curve to higher temperatures. ? It will not change the Tm at pH 3.0 because the Lys side chain pKa is 10.53. Suppose that the thermal denaturation experiment on the protein with the Met to Lys mutation took place at pH 10.0. Would the mutation have a greater or lesser impact on stability at pH 10.0 compared to pH 3.0? ? lesser, because a less acidic environment contributes to general protein stability ? lesser, because a greater fraction of Lys can remain buried in the core at pH 10.0 ? no change, because the Lys side chain pKa is above 10.0 so the side chain remains charged ? greater, because high pH values destabilize proteins$

Added by Johnny W.

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