Schimmel P
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
J Mol Evol. 1995 May;40(5):531-6. doi: 10.1007/BF00166621.
An operational RNA code relates specific amino acids to sequences/structures in RNA hairpin helices which reconstruct the seven-base-pair acceptor stems of transfer RNAs. These RNA oligonucleotides are aminoacylated by aminoacyl tRNA synthetases. The specificity and efficiency of aminoacylation are generally determined by three or four nucleotides which are near the site of amino acid attachment. These specificity-determining nucleotides include the so-called "discriminator base" and one or two base pairs within the first four base pairs of the helix. With three examples considered here, nucleotide sequence variations between the eubacterial E. coli tRNA acceptor stems and their human cytoplasmic and mitochondrial counterparts are shown to include changes of some of the nucleotides known to be essential for aminoacylation by the cognate E. coli enzymes. If the general locations of the specificity-determining nucleotides are the same in E. coli and human RNAs, these RNA sequence variations imply a similar covariation in sequences/structures of the E. coli and human tRNA synthetases. These covariations would reflect the integral relationship between the operational RNA code and the design and evolution of tRNA synthetases.
一种操作性RNA密码将特定氨基酸与RNA发夹螺旋中的序列/结构相关联，这些序列/结构可重构转运RNA的七碱基对受体茎。这些RNA寡核苷酸由氨酰tRNA合成酶进行氨酰化。氨酰化的特异性和效率通常由靠近氨基酸连接位点的三或四个核苷酸决定。这些决定特异性的核苷酸包括所谓的“判别碱基”以及螺旋前四个碱基对中的一或两个碱基对。通过这里考虑的三个例子表明，真细菌大肠杆菌tRNA受体茎与其人类细胞质和线粒体对应物之间的核苷酸序列差异包括一些已知对同源大肠杆菌酶进行氨酰化至关重要的核苷酸的变化。如果在大肠杆菌和人类RNA中决定特异性的核苷酸的大致位置相同，那么这些RNA序列差异意味着大肠杆菌和人类tRNA合成酶的序列/结构中存在类似的共变。这些共变将反映操作性RNA密码与tRNA合成酶的设计和进化之间的整体关系。
