Polarity of disulfide bonds.
Polarity of disulfide bonds.
复制标题
二硫键的极性。
DOI：
10.1002/pro.5560020713
复制
发表时间：
1993
期刊：
影响因子：
--
通讯作者：
Pielak,GJ
中科院分区：
文献类型：
--
作者：
Saunders,AJ;Young,GB;Pielak,GJ
蛋白质稳定性的定义是变性状态的自由能减去天然状态的自由能AGD。Flory(1956)提出，在变性状态下，二硫键通过降低链熵来增加AGD。或者，Doig和Williams(1991)提出，蛋白质通过二硫键增加的AGD主要是热变的。无论稳定的来源是什么，具有自然产生的二硫键的蛋白质比它们的非交联物更稳定(Pace等人，1988年)。然而，引入新的二硫化物并不总是稳定蛋白质(Betz&Pielak[1992]和其中的参考文献)。二硫键通常被埋在蛋白质中(Thorton，1981)，残基被埋的程度与它们的极性之间存在相关性(Rose等人，1985；Miller等人，1987)。因此，我们想知道两个半胱氨酸和一个半胱氨酸之间的极性差异是否在一定程度上解释了二硫键的稳定作用。为此，测定了半胱氨酸类似物甲基二硫化物(CH3-SS-CH3)在环己烷和H_20、x+H_20之间的分配系数。半胱氨酸类似物甲硫醇(CH3-SH)的&，x+HzO值由Radzicka和Wolfenden(1988)报道。作为对照，测定了甲基乙基硫醚(CH_3-CH_2-S-CH_3)的对数&，x-H_(20)，以便与Radzicka和Wolfenden报告的-1.73值进行比较。
Protein stability is defined as the free energy of denatured state minus that of the native state, AGd. Flory (1956) proposed that disulfide bonds increase AGd by decreasing chain entropy in the denatured state. Alternatively, Doig and Williams (1991) suggest that the increase in AGd of proteins by disulfide bonds is primarily enthalpic. Whatever the source of the stabilization, proteins with naturally occurring disulfide bonds are more stable than their noncross-linked equivalents (Pace et al., 1988). Introduction of novel disulfides, however, does not always stabilize proteins (Betz & Pielak [1992] and references therein).Disulfide bonds are often buried within proteins (Thorton, 1981), and there is a correlation between the extent that residues are buried and their polarity (Rose et al., 1985; Miller et al., 1987). Therefore, we wondered whether a difference in polarity between two cysteines and a cystine could account, in part, for the stabilizing effect of disulfide bonds. To this end, the distribution coefficient between cyclohexane and H20, &, x+ H20, of a cystine analog, methyl disulfide (CH3-SS-CH3), was measured. The &, x+ HzO value for the cysteine analog, methanethiol (CH3-SH), was reported by Radzicka and Wolfenden (1988). As a control, log &, x-H20 for ethyl methyl sulfide (CH3-CH2-S-CH3) was determined so that it could be compared to the value,-1.73, reported by Radzicka and Wolfenden.