Dvorak D J, Kidson C
J Biol Chem. 1976 Nov 10;251(21):6730-4.
The conformations of aminoacyl- and deacylated tRNA Phe (yeast) have been compared by using the steroid progesterone and the tetranucleotides U-C-C-C and C-G-A-A as probes of transfer RNA ordered structure. U-C-C-C is complementary to G18-G19-G20-A21 in the dihydrouridine loop and C-G-A-A is complementary to T54-psi55-C56-G57 in the ribosylthymine loop. None of the probes bound to deacylated tRNA Phe but all three bound to phenylalanyl-tRNA Phe, with molar association constants of the order of 10(4) M-1. The oligonucleotide binding data imply that the tertiary hydrogen bonds between G18 and psi55, G19 and C56, T54 and m1A58, and A21 and the ribose of U8 (Quigley, G. J., Wang, A. H. J., Seeman, N. C., Suddath, F. L., Rich, A., Sussman, J. L., and Kim, S. H., (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 4866-4870) are destabilized or broken on aminoacylation, unmasking the sequence T-psi-C-G thought to be involved in ribosome binding of aminoacyl-tRNA. The presumed progesterone binding site is G18-G19-G20, which is part of the binding site for U-C-C-C. Competition was not, however, observed between these two probes; model building has shown that they could, theoretically, bind simultaneously. Since progesterone bound to N-acetyl-Phe-tRNA Phe, the introduction of the additional positive charge on aminoacylation is not sufficient per se to explain the conformational change. The association of progesterone with peptidyl-tRNA Phe was similar to that with aminoacyl-tRNA Phe, implying that no further conformational change takes place in the region of the steroid binding site on formation of a peptide bond.
通过使用类固醇孕酮以及四核苷酸U-C-C-C和C-G-A-A作为转移RNA有序结构的探针，对氨酰化和去酰化的苯丙氨酰tRNA（酵母）的构象进行了比较。U-C-C-C与二氢尿嘧啶环中的G18-G19-G20-A21互补，C-G-A-A与核糖胸腺嘧啶环中的T54-ψ55-C56-G57互补。没有一种探针能与去酰化的苯丙氨酰tRNA结合，但这三种探针都能与苯丙氨酰-tRNA结合，其摩尔缔合常数约为10⁴ M⁻¹。寡核苷酸结合数据表明，G18与ψ55、G19与C56、T54与m¹A58以及A21与U8核糖之间的三级氢键（Quigley, G. J., Wang, A. H. J., Seeman, N. C., Suddath, F. L., Rich, A., Sussman, J. L., and Kim, S. H., (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 4866 - 4870）在氨酰化时不稳定或断裂，从而暴露了被认为参与氨酰-tRNA核糖体结合的T-ψ-C-G序列。推测的孕酮结合位点是G18-G19-G20，它是U-C-C-C结合位点的一部分。然而，在这两种探针之间未观察到竞争；模型构建表明，理论上它们可以同时结合。由于孕酮与N-乙酰苯丙氨酰-tRNA结合，氨酰化时额外正电荷的引入本身不足以解释构象变化。孕酮与肽基-tRNA的缔合与与氨酰-tRNA的缔合相似，这意味着在形成肽键时，类固醇结合位点区域没有发生进一步的构象变化。
