Interaction of tRNA with antitumor polyamine analogues

We studied the interaction between tRNA and three polyamine analogues (1,1 1-diamino-4,8-diazaundecane center dot 4HCl (333), 3,7,11,15-tetrazaheptadecane center dot 4HCl (BE-333), and 3,7,11,15,19-pentazahenicosane center dot 5HCl (BE-3333)) using FTIR, UV-visible, and CD spectroscopic methods. Spectroscopic evidence showed that polyamine analogues bound tRNA via guanine N7, adenine, uracil O-2, and the backbone phosphate (PO2-) groups, while the most reactive sites for biogenic polyamines were guanine N7/O6, adenine N7, uracil O-2, and sugar 2'-OH groups as well as the backbone phosphate group. The binding constants of polyamine analogue-tRNA recognition were lower than those of the biogenic polyamine-tRNA complexes, with K-333 = 2.8 (+/- 0.5) x 10(4), KBE-333 = 3.7 (+/- 0.7) x 10(4), KBE-3333 = 4.0 (+/- 0.9) x 10(4), K-spm = 8.7 (+/- 0.9) x 10(5), K-spd = 6.1 (+/- 0.7) x 10(-5), and K-put = 1.0 (+/- 0.3) x 10(5) mol/L. tRNA remained in the A-family conformation, however, it aggregated at high polyamine analogue concentrations.