Abdurashidova G G, Tsvetkova E A, Budowsky E I
Zelinsky Institute of Organic Chemistry, USSR Academy of Sciences, Moscow.
Nucleic Acids Res. 1991 Apr 25;19(8):1909-15. doi: 10.1093/nar/19.8.1909.
Nucleotide residues in E. coli tRNA(Phe) interacting directly with proteins in pre- and posttranslocated ribosomal complexes have been identified by UV-induced cross-linking. In the tRNA(Phe) molecule located in the Ab-site (pretranslocated complex) residues A9, G18, A26 and U59 are cross-linked with proteins S10, L27, S7 and L2, respectively. In tRNA(Phe) located in the Pt-site (posttranslocated complex) residues C17, G44, C56 and U60 are cross-linked with proteins L2, L5, L27 and S9, respectively. The same cross-links (except for G44-L5) have been found for tRNA in the Pb-site of the pretranslocated ribosomal complex. None of the tRNA(Phe) residues cross-linked with proteins in the complexes examined by us are involved in the stabilization of the secondary structure, but residues A9, G18, A26, G44 and C56 participate in stabilization of tRNA tertiary structure. Since translocation of tRNA(Phe) from Ab- to P-site is accompanied by changes of tRNA contacts with proteins L2 and L27, we postulate that this translocation is coupled with tRNA turn around the axis joining the anticodon loop with the CCA-end of the molecule. This is in agreement with the idea about the presence of a kink in mRNA between codons located in the ribosomal A- and P-sites. In all E. coli tRNAs with known primary structure positions 18 and 56, interacting with L27 protein, when tRNA is located either in A- or P-site, are invariant, whereas positions 17 and 60, interacting with proteins only when tRNA is in the P-site, are strongly conserved. In positions 9, 26 and 59 purines are the preferred residues. In most E. coli tRNAs deviations from the consensus in these three positions is strongly correlated.
通过紫外线诱导交联，已鉴定出大肠杆菌苯丙氨酸转运RNA（tRNA(Phe)）中与易位前和易位后核糖体复合物中的蛋白质直接相互作用的核苷酸残基。位于A位（易位前复合物）的tRNA(Phe)分子中，残基A9、G18、A26和U59分别与蛋白质S10、L27、S7和L2交联。位于P位（易位后复合物）的tRNA(Phe)中，残基C17、G44、C56和U60分别与蛋白质L2、L5、L27和S9交联。在易位前核糖体复合物的P位中，tRNA也发现了相同的交联（G44-L5除外）。在我们检测的复合物中，与蛋白质交联的tRNA(Phe)残基均不参与二级结构的稳定，但残基A9、G18、A26、G44和C56参与tRNA三级结构的稳定。由于tRNA(Phe)从A位移至P位伴随着tRNA与蛋白质L2和L27接触的变化，我们推测这种易位与tRNA围绕连接反密码子环与分子CCA末端的轴的转动有关。这与核糖体A位和P位密码子之间的mRNA中存在扭结的观点一致。在所有已知一级结构的大肠杆菌tRNA中，当tRNA位于A位或P位时，与L27蛋白相互作用的第18位和第56位是不变的，而仅当tRNA位于P位时与蛋白质相互作用的第17位和第60位则高度保守。在第9、26和59位，嘌呤是首选残基。在大多数大肠杆菌tRNA中，这三个位置与共有序列的偏差高度相关。
