[A study of the conformation of tRNA(IAGLeu) from the cow mammary gland using chemical modification methods]

The nucleosides of tRNA(IAGLeu) (with a long variable loop) from the cow mammary gland included in formation of the three-dimensional structure have been analysed by the chemical modification methods. Exposed guanosine and cytidine residues were detected by means of dimethylsulfate, whereas diethylpyrocarbonate was used to detect exposed adenosine residues. The low level of the modification was characteristic of guanosine residues in positions 10 (m2G), 13, 15, 23, 24, 29, 30, 47 H, 51, 52, 53, 57; of cytidine residues in positions 48 (m5C), 56 and those involved in Watson--Crick pairing; of adenosine residues in positions 14, 22, 31, 42, 59, 64. Most bases of tRNA(IAGLeu) thus detected are similarly located in the yeast tRNA(Phe) molecule, which suggests a common role of these bases in the formation of the spacial structure of both tRNAs.