On the conformation of transfer RNA in solution: Dependence of denaturation temperature and structural parameters of mixed and formylmethionyl Escherichia coli transfer RNA on sodium ion concentration☆

摘要: Abstract There is at present considerable evidence that transfer RNA in the presence of Mg 2+ exists a more highly ordered state than predicted by simple cloverleaf models (Levitt, 1969; Cramer, 1970, Abstr. 8th Internat. Cong. Biochem. p. 214; 1971). This structure shown here to correspond closely found high concentrations Na + (2 m ) pH 6.5. As counterion concentration decreased, progressive denaturation occurs finally approximating coil. We have determined dependence mid-point thermal profiles ( T ), ultraviolet absorbance, viscosity, circular dichroism spectra, and tritium exchange-out rates number on for both unfractionated (mixed) Escherichia coli tRNA as well purified E. formylmethionine specific tRNA. The transition physical data are consistent with interpretation states function ionic strength. Specifically, 6.5 region 0.1 2 -NaCl, below 25 °C, varying degrees superstructure converging state. Below -Na itself takes place, representing electrostatically induced some type coil configuration. In vicinity we suggest average solution approximates conformation, although no information distribution molecules among related states. picture provides useful reference functional studies, which may define completely tertiary conformation biological interactions this molecule.