Pace C N
Department of Medical Biochemistry and Genetics, Texas A&M University, College Station 77843-1114.
J Mol Biol. 1992 Jul 5;226(1):29-35. doi: 10.1016/0022-2836(92)90121-y.
The decrease in conformational stability, delta(delta G), has been measured for 72 aliphatic side-chain mutants from four proteins in which a larger side-chain is replaced by a smaller side-chain so that steric effects are minimal. When these delta(delta G) values are corrected to the same accessibility, namely 100% buried, then the following -delta(delta G) values per -CH2- group (in kcal/mol) are obtained: Ile----Val (1.26), Ala (1.26), Gly (1.26); Leu----Ala (1.16), Gly (1.21); Val----Ala (1.23), Gly (1.53). The average of these values is 1.27(+/- 0.07) kcal/mol. The 72 individual values range from 0 to 2.4 kcal/mol with an average value of 1.27(+/- 0.51) (standard deviation) kcal/mol. When the delta Gtr values from n-octanol to water are corrected for the difference in volume between the solutes and the solvents, the average value for the same substitutions is 1.25(+/- 0.05) kcal/mol. This suggests that proteins gain 1.3(+/- 0.5) kcal/mol in stability for each -CH2- group buried in folding, and, furthermore, that the volume corrected delta Gtr values for n-octanol for the amino acid side-chains provide good estimates of the contribution of the hydrophobic effect to globular protein stability.
已对来自四种蛋白质的72个脂肪族侧链突变体的构象稳定性降低值（Δ（ΔG））进行了测定，在这些突变体中，较大的侧链被较小的侧链取代，以使空间效应最小化。当将这些Δ（ΔG）值校正到相同的可及性，即100%埋藏时，可得到每个-CH₂-基团的以下-Δ（ΔG）值（以kcal/mol为单位）：异亮氨酸→缬氨酸（1.26）、丙氨酸（1.26）、甘氨酸（1.26）；亮氨酸→丙氨酸（1.16）、甘氨酸（1.21）；缬氨酸→丙氨酸（1.23）、甘氨酸（1.53）。这些值的平均值为1.27（±0.07）kcal/mol。这72个个体值的范围为0至2.4 kcal/mol，平均值为1.27（±0.51）（标准差）kcal/mol。当将正辛醇到水的ΔGtr值校正溶质和溶剂之间的体积差异时，相同取代的平均值为1.25（±0.05）kcal/mol。这表明，蛋白质在折叠过程中每埋藏一个-CH₂-基团，稳定性增加1.3（±0.5）kcal/mol，此外，氨基酸侧链的正辛醇体积校正后的ΔGtr值能很好地估计疏水效应对球状蛋白质稳定性的贡献。
