The hemK gene in Escherichia coli encodes the N5-glutamine methyltransferase that modifies peptide release factors
The hemK gene in Escherichia coli encodes the N5-glutamine methyltransferase that modifies peptide release factors
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DOI：
10.1093/emboj/21.4.769
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发表时间：
2002-02-15
期刊：
影响因子：
11.4
通讯作者：
Buckingham, RH
中科院分区：
文献类型：
--
作者：
Heurgué-Hamard, V;Champ, S;Buckingham, RH
大肠杆菌中的1类肽释放因子（RF）在普遍保守的GGQ基序的谷氨酰胺残基上被N（5）-甲基化。另一种单独的蛋白质已被证明含有N（5）-甲基谷氨酰胺：E。大肠杆菌核糖体蛋白L3。我们确定的L3甲基转移酶YfcB，并表明它甲基化核糖体从yfcB菌株在体外，但不是RF 1或RF 2。HemK是YfcB的直系同源物，在体外可甲基化RF 1和RF 2。hemK紧邻prfA的下游并与prfA共表达。在E. coli K12在丰富培养基上的生长非常差，并消除了RF 1的甲基化。来自K12菌株的未甲基化的RF 2的活性极低，这是由于在位置246处的苏氨酸代替存在于所有其它细菌RF中的丙氨酸或丝氨酸的累积效应，以及缺乏Gln 252的N（5）-甲基化。hemK K12菌株中快速生长的自发回复突变体在RF 2中含有突变Thr 246 Ala或Thr 246 Ser。HemK和YfcB是最早发现的修饰谷氨酰胺的甲基转移酶，并且广泛分布于自然界中。
Class 1 peptide release factors (RFs) in Escherichia coli are N(5)-methylated on the glutamine residue of the universally conserved GGQ motif. One other protein alone has been shown to contain N(5)-methylglutamine: E. coli ribosomal protein L3. We identify the L3 methyltransferase as YfcB and show that it methylates ribosomes from a yfcB strain in vitro, but not RF1 or RF2. HemK, a close orthologue of YfcB, is shown to methylate RF1 and RF2 in vitro. hemK is immediately downstream of and co-expressed with prfA. Its deletion in E. coli K12 leads to very poor growth on rich media and abolishes methylation of RF1. The activity of unmethylated RF2 from K12 strains is extremely low due to the cumulative effects of threonine at position 246, in place of alanine or serine present in all other bacterial RFs, and the lack of N(5)-methylation of Gln252. Fast-growing spontaneous revertants in hemK K12 strains contain the mutations Thr246Ala or Thr246Ser in RF2. HemK and YfcB are the first identified methyltransferases modifying glutamine, and are widely distributed in nature.