Class I and class II lysyl-tRNA synthetase mutants and the genetic encoding of pyrrolysine in Methanosarcina spp.
Class I and class II lysyl-tRNA synthetase mutants and the genetic encoding of pyrrolysine in Methanosarcina spp.
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DOI：
10.1111/j.1365-2958.2007.05740.x
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发表时间：
2007-06-01
影响因子：
3.6
通讯作者：
Krzycki, Joseph A.
中科院分区：
文献类型：
--
作者：
Mahapatra, Anirban;Srinivasan, Gayathri;Krzycki, Joseph A.
甲烷八叠球菌开始用甲基转移酶从甲胺产生甲烷，所述甲基转移酶通过将UAG翻译为吡咯赖氨酸而产生。体外证据表明吡咯赖氨酰-tRNA（Pyl）的两种可能途径。PylS将吡咯赖氨酸连接至tRNA（Pyl）。或者，I类和II类赖氨酰-tRNA合成酶（LysRS 1和LysRS 2）一起形成赖氨酰-tRNA（Pyl），其为吡咯赖氨酰-tRNA（Pyl）的潜在中间体。甲烷八叠球菌LysRS 1和LysRS 2的不寻常的拥有。也可以反映催化性能的差异。在这里，我们评估了这些假设的体内相关性。lysK和mtmB的成绩单，编码LysRS 1和单甲胺甲基转移酶，可检测到甲烷八叠球菌巴氏在早期对数生长的三甲胺，但不是甲醇。相比之下，编码LysRS 2的lysS转录物在对数期期间用任一底物都是可检测的。具有lysK或lysS缺失的嗜乙酸甲烷八叠球菌菌株在具有野生型水平的单甲胺甲基转移酶和氨酰-tRNA（Pyl）的甲醇和甲胺上正常生长。在采用tRNA（Pyl）抑制UAG的重组系统中，lysK和lysS基因无法取代pylS。这些结果支持LysRS 1与甲胺上生长的关联，但不是LysRS 1/LysRS 2在吡咯赖氨酸的遗传编码中的重要作用。然而，在lysS突变体中减少的赖氨酰-tRNA（Lys）为细菌lysS基因稳定转移至甲烷古菌提供了可能的理由。
Methanosarcina spp. begin methanogenesis from methylamines with methyltransferases made via the translation of UAG as pyrrolysine. In vitro evidence indicates two possible routes to pyrrolysyl-tRNA(Pyl). PylS ligates pyrrolysine to tRNA(Pyl). Alternatively, class I and class II lysyl-tRNA synthetases (LysRS1 and LysRS2) together form lysyl-tRNA(Pyl), a potential intermediate to pyrrolysyl-tRNA(Pyl). The unusual possession of both LysRS1 and LysRS2 by Methanosarcina spp. may also reflect differences in catalytic properties. Here we assessed the in vivo relevance of these hypotheses. The lysK and mtmB transcripts, encoding LysRS1 and monomethylamine methyltransferase, were detectable in Methanosarcina barkeri during early log growth on trimethylamine, but not methanol. In contrast, lysS transcript encoding LysRS2 was detectable during log phase with either substrate. Methanosarcina acetivorans strains bearing deletions of lysK or lysS grew normally on methanol and methylamines with wild-type levels of monomethylamine methyltransferase and aminoacyl-tRNA(Pyl). The lysK and lysS genes could not replace pylS in a recombinant system employing tRNA(Pyl) for UAG suppression. The results support an association of LysRS1 with growth on methylamine, but not an essential role for LysRS1/LysRS2 in the genetic encoding of pyrrolysine. However, decreased lysyl-tRNA(Lys) in the lysS mutant provides a possible rationale for stable transfer of the bacterial lysS gene to methanoarchaea.