Baindur S R, Douglas K T
Biochim Biophys Acta. 1987 Jan 20;923(1):66-73. doi: 10.1016/0304-4165(87)90127-9.
As an extension of work on the inhibition of enzymes by arylthallium(III) reagents, the thallium analogues of the organomercurials, we have studied the interactions of these molecules with transfer RNA. In contrast to thallous acetate, thallium(III) derivatives (thallic trifluoroacetate, p-methylphenylthallium(III) bis-trifluoroacetate (MPT) and o-carboxyphenylthallium(III) bis-trifluoroacetate) bound to Escherichia coli tRNA. The interaction was fully reversible upon Sephadex G-25 gel filtration, and binding constants and stoichiometries were evaluated by a number of procedures. The likely site of interaction was shown to be the thiouridine residue (s4U8) based on changes induced by MPT on the absorbance around 330 nm. No changes in stacking interactions could be detected from the absorption or circular dichroic spectra. The detailed structure of the groups on thallium(III) affected the interaction with tRNA. Thalliation at s4U8 affects the absorbance at 335 nm and the amino-acid uptake capacity of E. coli tRNAPhe in parallel, the latter being progressively inhibited by increasing amounts of MPT. In a model nucleoside system, uridine disulphide is probably formed from reduced thiouridine by the oxidative action of the Tl(III) reagents. No evidence of cross-linking of E. coli tRNA molecules under gel electrophoretic conditions was obtained in contrast to the model nucleoside. The easily reversible interaction of MPT with sulphur sites in E. coli tRNA contrasts with the stable (to gel filtration) bonds formed between MPT and (thiol) sites in enzymes.
作为芳基铊（III）试剂对酶抑制作用研究工作的延伸，即有机汞化合物的铊类似物，我们研究了这些分子与转运RNA的相互作用。与醋酸亚铊不同，铊（III）衍生物（三氟乙酸铊、对甲基苯基铊（III）双三氟乙酸盐（MPT）和邻羧基苯基铊（III）双三氟乙酸盐）与大肠杆菌转运RNA结合。通过Sephadex G - 25凝胶过滤，这种相互作用是完全可逆的，并且通过多种方法评估了结合常数和化学计量。基于MPT对330nm左右吸光度的影响，表明相互作用的可能位点是硫代尿苷残基（s4U8）。从吸收光谱或圆二色光谱中未检测到堆积相互作用的变化。铊（III）上基团的详细结构影响与转运RNA的相互作用。s4U8处的铊化平行地影响335nm处的吸光度和大肠杆菌苯丙氨酸转运RNA的氨基酸摄取能力，后者随着MPT量的增加而逐渐受到抑制。在模型核苷系统中，尿苷二硫化物可能由还原的硫代尿苷通过Tl（III）试剂的氧化作用形成。与模型核苷相比，在凝胶电泳条件下未获得大肠杆菌转运RNA分子交联的证据。MPT与大肠杆菌转运RNA中硫位点的易可逆相互作用与MPT和酶中（硫醇）位点形成的稳定（对凝胶过滤）键形成对比。
