MISCHARGING MUTANTS OF SU+-2 GLUTAMINE TRANSFER-RNA IN ESCHERICHIA-COLI .1. MUTATIONS NEAR THE ANTICODON CAUSE MISCHARGING
MISCHARGING MUTANTS OF SU+-2 GLUTAMINE TRANSFER-RNA IN ESCHERICHIA-COLI .1. MUTATIONS NEAR THE ANTICODON CAUSE MISCHARGING
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DOI：
10.1266/jjg.63.237
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发表时间：
1988-06-01
期刊：
影响因子：
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通讯作者：
OZEKI, H
中科院分区：
文献类型：
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作者：
YAMAO, F;INOKUCHI, H;OZEKI, H
为了筛选Su+2谷氨酰胺tRNA的错电荷突变体，对E. coli K12中筛选出Su+2不能特异性抑制的菌株。通过利用这些突变体，cysam 235和metam 3，几十个Su+2的误充电突变体被分离出来，因为那些赋予改变的抑制模式的一组测试琥珀突变体的细菌和大肠杆菌。核苷酸序列分析显示，发现突变位点仅在位于反密码子环3“-末端的ψ 37残基处，将其变为A37或C37。这些突变体作为抑制cysam 235而不是metam 3的突变体获得。从这些中，选择次级突变体。在这些突变体中，通过能够抑制metam 3的额外碱基取代进一步改变了抑制模式。这些突变体仅从A37而不是从C37突变体tRNA获得。发现A37的其他突变是A29或C38，它们位于反密码子茎中最低的两个碱基对。Su+2谷氨酰胺tRNA的错电荷位点位于新检测到的tRNA区域，不同于先前的Su+3酪氨酸或Su+7色氨酸tRNA的情况。这一发现的含义进行了讨论L形tRNA分子与氨酰-tRNA合成酶的识别。由双突变体A37 A29和A37 C38给出的抑制模式与突变体tRNA与异丙基-tRNA合成酶相互作用的观察结果一致。
In order to select the mischarging mutants of Su+2 glutamine tRNA, auxotrophic amber mutants of E. coli K12 which cannot be suppressed particularly by Su+2 were screened. By utilizing these mutants, cysam235 and metam3, several tens of mischarging mutants of Su+2 were isolated, as those conferring altered suppression patterns for a set of tester amber mutants of bacteria and phages. Nucleotide sequence analysis revealed that the mutation sites were found to be exclusively at .psi.37 residue located at the 3''-end of anticodon loop, changing it to either A37 or C37. These mutants were obtained as those suppressing cysam235, and not metam3. From these, secondary mutants were selected. In these mutants suppression patterns were further altered by the additional base substitutions, capable of suppressing metam3. Such mutants were obtained exclusively from A37 and not from C37 mutant tRNA. Additional mutations to A37 were found to be either A29 or C38, which are located at the lowermost two base pairs i anticodon stem. The mischarging sites in Su+2 glutamine tRNA locate in the newly detected region of tRNA, differing from the previous case of Su+3 tyrosine or Su+7 tryptophan tRNAs. Implication of this finding is dicussed on L-shaped tRNA molecule in relation to aminoacyl-tRNA synthetase recognition. Suppression patterns given by the double-mutants, A37A29 and A37C38, were consistent with the observation that the mutant tRNAs interact with tryptophanyl-tRNA synthetase.