Chaperonin overexpression promotes genetic variation and enzyme evolution
Chaperonin overexpression promotes genetic variation and enzyme evolution
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DOI：
10.1038/nature08009
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发表时间：
2009-06-04
期刊：
影响因子：
64.8
通讯作者：
Tawfik, Dan S.
中科院分区：
文献类型：
--
作者：
Tokuriki, Nobuhiko;Tawfik, Dan S.
大多数蛋白质突变，特别是改变蛋白质功能的突变，破坏了稳定性，因此是有害的。伴侣蛋白或热休克蛋白通常与缓冲突变有关，因此可以促进中性遗传多样性的获得和适应速度。我们研究了大肠杆菌GroEL/GroES伴侣蛋白缓冲不稳定和适应性突变的能力。在这里，我们表明，在体外用四种不同的酶进行的突变漂移表明，GroEL/GroES过表达使累积突变的数量增加了一倍，并促进了携带蛋白质核心突变和/或具有更高去稳定作用的突变的酶变体的折叠。（平均>3.5 kcal mol（-1）的去稳定化能量，而在不存在GroEL/GroES的情况下，类似于1 kcal mol（-1））。在GroEL/GroES过表达下，修饰的酶特异性的分歧发生得快得多，就适应变体的数量（>= 2倍）及其改进的特异性和活性（>= 10倍）而言。这些结果表明，蛋白质的稳定性是蛋白质进化的一个主要限制，缓冲机制，如伴侣蛋白是缓解这种限制的关键。
Most protein mutations, and mutations that alter protein functions in particular, undermine stability and are therefore deleterious. Chaperones, or heat-shock proteins, are often implicated in buffering mutations, and could thus facilitate the acquisition of neutral genetic diversity and the rate of adaptation. We examined the ability of the Escherichia coli GroEL/GroES chaperonins to buffer destabilizing and adaptive mutations. Here we show that mutational drifts performed in vitro with four different enzymes indicated that GroEL/GroES overexpression doubled the number of accumulating mutations, and promoted the folding of enzyme variants carrying mutations in the protein core and/or mutations with higher destabilizing effects (destabilization energies of >3.5 kcal mol(-1), on average, versus, similar to 1 kcal mol(-1) in the absence of GroEL/GroES). The divergence of modified enzymatic specificity occurred much faster under GroEL/GroES overexpression, in terms of the number of adapted variants (>= 2-fold) and their improved specificity and activity (>= 10-fold). These results indicate that protein stability is a major constraint in protein evolution, and buffering mechanisms such as chaperonins are key in alleviating this constraint.