aKMT Catalyzes Extensive Protein Lysine Methylation in the Hyperthermophilic Archaeon Sulfolobus islandicus but is Dispensable for the Growth of the Organism
aKMT Catalyzes Extensive Protein Lysine Methylation in the Hyperthermophilic Archaeon Sulfolobus islandicus but is Dispensable for the Growth of the Organism
复制标题
aKMT 催化超嗜热古细菌岛硫化叶菌中广泛的蛋白质赖氨酸甲基化，但对于该生物体的生长是可有可无的
DOI：
10.1074/mcp.m115.057778
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发表时间：
2016-09-01
影响因子：
7
通讯作者：
Huang, Li
中科院分区：
文献类型：
--
作者：
Chu, Yindi;Zhu, Yanping;Huang, Li
蛋白质甲基化被认为广泛存在于Creanarchaea中。最近，aKMT，一个高度保守的crenarchaeal蛋白赖氨酸甲基转移酶，被确定并显示出广泛的底物特异性在体外。在这里，我们已经构建了一个aKMT缺失突变体的极端嗜热crenarcheon硫化叶菌islandicus。该突变体是可行的，但显示出比亲本菌株在非最佳生长条件下的生长速率适度较慢。与缺乏aKMT对细胞生长的中等影响一致，与亲本菌株相比，突变菌株中编码底物转运、能量代谢、转录调节、应激反应蛋白等推定功能的少量基因的表达差异调节超过两倍。通过质谱分析总细胞蛋白的甲基化，发现亲本和突变株中甲基化蛋白分别约占鉴定蛋白的2/3（1，158/1，751）和1/3（591/1，757），表明S. islandicus，aKMT是该生物体中主要蛋白质甲基转移酶。在aKMT的甲基化位点没有检测到显著的序列偏好。当在结构中可见时，甲基化赖氨酸残基全部位于蛋白质的表面上。与S-腺苷-L-甲硫氨酸（SAM）或S-腺苷高半胱氨酸（SAH）复合的aKMT的晶体结构显示，该蛋白质由四个螺旋和七个片层组成，缺乏在PrmA（aKMT的细菌同系物）中发现的底物识别结构域，与aKMT的广泛底物特异性一致。我们的研究结果表明，在某些非最佳条件下，aKMT可能在维持生物体有效生长所需的细胞蛋白的甲基化状态方面发挥作用。
Protein methylation is believed to occur extensively in creanarchaea. Recently, aKMT, a highly conserved crenarchaeal protein lysine methyltransferase, was identified and shown to exhibit broad substrate specificity in vitro. Here, we have constructed an aKMT deletion mutant of the hyperthermophilic crenarchaeon Sulfolobus islandicus. The mutant was viable but showed a moderately slower growth rate than the parental strain under non-optimal growth conditions. Consistent with the moderate effect of the lack of aKMT on the growth of the cell, expression of a small number of genes, which encode putative functions in substrate transportation, energy metabolism, transcriptional regulation, stress response proteins, etc, was differentially regulated by more than twofold in the mutant strain, as compared with that in the parental strain. Analysis of the methylation of total cellular protein by mass spectrometry revealed that methylated proteins accounted for approximate to 2/3 (1,158/1,751) and approximate to 1/3 (591/1,757) of the identified proteins in the parental and the mutant strains, respectively, indicating that there is extensive protein methylation in S. islandicus and that aKMT is a major protein methyltransferase in this organism. No significant sequence preference was detected at the sites of methylation by aKMT. Methylated lysine residues, when visible in the structure, are all located on the surface of the proteins. The crystal structure of aKMT in complex with S-adenosyl-l-methionine (SAM) or S-adenosyl homocysteine (SAH) reveals that the protein consists of four helices and seven sheets, lacking a substrate recognition domain found in PrmA, a bacterial homolog of aKMT, in agreement with the broad substrate specificity of aKMT. Our results suggest that aKMT may serve a role in maintaining the methylation status of cellular proteins required for the efficient growth of the organism under certain non-optimal conditions.