[Binding of the yeast phenylalanine tRNA with Escherichia coli ribosomes. Effect of the removal of a modified base from the 3'-end of the anticodon on codon-anticodon interaction]

Abstract

Phe-tRNAPhe+Y and N-acetyl-Phe-tRNAPhe+Y from yeast interact with prokaryotic 30S subunits and 70S ribosomes with slightly lower affinity than respective tRNA's of E. coli (decrease of standard free energy change of interaction less than 10%). The removal of Y-base from Phe-tRNAPhe+Y results in two orders of magnitude decrease of association constant of Phe-tRNAPh-Ye with P site of the 30S X poly(U) complex and one ordef of magnitude or more of that with A site. The same modification decreases the association constants of Phe-tRNAPhe-Y and N-acetyl-Phe-tRNAPhe-Y 60 and 15 times respectively with P site of the 70S X poly(U) complex. In the absence of poly(U) the affinity of N-acetyl-Phe-tRNAPhe-Y to P-site of 70S ribosome was 20-fold lower than that of native N-acetyl-Phe-tRNAPhe+Y. The sign of interaction enthalpy of N-acetyl-Phe-tRNAPhe+/-Y and Phe-tRNAPhe-Y changes below 6-7 degrees C exposing the hydrophobic part of P-site interactions. Similar removal of Y-base does not change both the enthalpy of interaction with P-site and magnesium concentration dependence.