The L-isoaspartyl protein repair methyltransferase enhances survival of aging Escherichia coli subjected to secondary environmental stresses.
The L-isoaspartyl protein repair methyltransferase enhances survival of aging Escherichia coli subjected to secondary environmental stresses.
复制标题
L-异天冬氨酰蛋白修复甲基转移酶可增强遭受二次环境胁迫的老化大肠杆菌的存活率。
DOI：
10.1128/jb.180.10.2623-2629.1998
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发表时间：
1998
影响因子：
3.2
通讯作者：
Clarke,S
中科院分区：
文献类型：
--
作者：
Visick,JE;Cai,H;Clarke,S
大肠杆菌的pcm基因编码的β-异戊酰基蛋白修复甲基转移酶，与其在生物界的同源物一样，可以将蛋白质中的异常异戊酰基残基（由天冬酰胺酰或戊酰基残基自发形成）转化为正常的戊酰基残基。据报道，pcm基因突变会大大降低细胞在稳定期的存活率，当细胞受到热或渗透压胁迫时（C。Li和S. Clarke，Proc. Natl. Acad. Sci. USA 89：9885-9889，1992）。然而，我们随后证明这些菌株在rpoS中有一个二级突变，它编码一个静止期特异性σ因子（J. E. Visick和S. Clarke，J. Bacteriol. 179：4158-4163，1997）。我们现在表明，therpoSmaturation，导致90%的HPII过氧化氢酶活性下降，可以解释以前观察到的表型。我们进一步证明了一个新的pcm突变体缺乏这些表型。有趣的是，新构建的pcm突变体，当长时间保持在稳定期时，对环境胁迫敏感，包括暴露于甲醇，百草枯产生氧自由基，高盐浓度和重复加热至42°C。pcmmutation还导致在稳定期细胞中的竞争劣势。所有这些表型都可以通过整合在染色体其他地方的功能性pcm基因来补充。这些数据表明，蛋白质变性和异戊酰形成可能协同作用，以损害老化E。大肠杆菌中，修复甲基转移酶可以发挥作用，限制积累的潜在破坏性的异戊酰残基在体内。
Like its homologs throughout the biological world, thel-isoaspartyl protein repair methyltransferase ofEscherichia coli, encoded by thepcmgene, can convert abnormall-isoaspartyl residues in proteins (which form spontaneously from asparaginyl or aspartyl residues) to normal aspartyl residues. Mutations inpcmwere reported to greatly reduce survival in stationary phase and when cells were subjected to heat or osmotic stresses (C. Li and S. Clarke, Proc. Natl. Acad. Sci. USA 89:9885–9889, 1992). However, we subsequently demonstrated that those strains had a secondary mutation inrpoS, which encodes a stationary-phase-specific sigma factor (J. E. Visick and S. Clarke, J. Bacteriol. 179:4158–4163, 1997). We now show that therpoSmutation, resulting in a 90% decrease in HPII catalase activity, can account for the previously observed phenotypes. We further demonstrate that a newpcmmutant lacks these phenotypes. Interestingly, the newly constructedpcmmutant, when maintained in stationary phase for extended periods, is susceptible to environmental stresses, including exposure to methanol, oxygen radical generation by paraquat, high salt concentrations, and repeated heating to 42°C. Thepcmmutation also results in a competitive disadvantage in stationary-phase cells. All of these phenotypes can be complemented by a functionalpcmgene integrated elsewhere in the chromosome. These data suggest that protein denaturation and isoaspartyl formation may act synergistically to the detriment of agingE. coliand that the repair methyltransferase can play a role in limiting the accumulation of the potentially disruptive isoaspartyl residues in vivo.