Premium
The structure of the anticodon loop of tRNA Phe from yeast as deduced from spectroscopic studies on oligonucleotides
Author(s) -
Maelicke Alfred,
Von Der Haar Friedrich,
Sprinzl Mathias,
Cramer Friedrich
Publication year - 1975
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1975.360140112
Subject(s) - transfer rna , chemistry , oligonucleotide , circular dichroism , stacking , fluorescence , nucleobase , crystallography , base pair , stereochemistry , rna , dna , biochemistry , gene , physics , organic chemistry , quantum mechanics
The hexanucleotide Gm‐A‐A‐Y‐A‐ψp excised from the anticodon loop of yeast tRNA Phe and its constituent oligonucleotides have been studied by ultraviolet absorption spectroscopy, static fluorescence, and circular dichroism. Gm‐Ap has a melting point of 45°C and a high melting enthalpy when compared with G‐Ap; hence 2′‐O‐methylation seems to stabilize stacking interactions. The nucleobase Y adjacent to the 3′‐side of the anticodon triplet interacts stronger with its 3′‐neighboring A than with its 5′‐neighboring A. It is concluded that the base Y disconnects the stack of the anticodon itself from the stack of the anticodon stem, thereby setting a reading frame for the mRNA in the course of protein biosynthesis. From the opposite signs of the short‐wavelength Cotton effects in the spectra of Gm‐A‐A‐Y‐Ap and Gm‐A‐A‐Y, it is concluded that Y after removal of its 3′ neighbor undergoes a dramatic change in its conformation. The fluorescence of the nucleobase Y upon addition of Mg 2+ is enhanced in oligonucleotides longer than two. An identical enhancement is observed for tRNA Phe , indicating that this Mg 2+ effect is a property of an oligonucleotide segment and does not reflect conformational changes of the whole tRNA. The data presented here reveal that the basic structural features of the anticodon loop are already present in the hexanucleotide Gm‐A‐A‐Y‐A‐ψp and are not determined by the overall structure of tRNA.