Oxovanadium Ions Bind Transfer RNA at Multiple Sites

Abstract

Oxovanadium compounds exert preventive effects against chemical carcinogenesis in animals and form complexes with DNA and RNA in vivo. This study was designed to examine the interaction of transfer RNA (tRNA) with VO(2+) and VO₃⁻ ions in aqueous solution at physiological pH, with constant a tRNA concentration of 12.5 mM and different vanadium/RNA (P) (P = phosphate) molar ratios (r) of 1:60 to 1:2. Affinity capillary electrophoresis and Fourier transform infrared spectroscopy were used to determine the ion-binding site, the binding constant, and tRNA conformation in oxovanadium-RNA complexes. Structural analysis showed that VO(2+) binds tRNA through guanine, adenine N7, and uracil O2 as well as to the backbone PO(2) group with apparent binding constants of K(G) = 8.9 (+/-1.2) x 10(4) M(-1) and K(U) = 3.4 (+/-0.85) x 10(4) M(-1). VO₃⁻ shows weaker binding through guanine and adenine bases with K = 4.6 (+/-0.95) x 10(4) M(-1) and no interaction with the backbone phosphate group. No tRNA conformational transition was observed upon vanadium complexation, whereas biopolymer aggregation occurred at high oxovanadium concentrations.