Abstract

Effects of divalent cations on self-splicing inhibition by the antibiotic spectinomycin of the phage T4 thymidylate synthase intro (td) have been investigated. Ca^2+ ion at 1mM concentration suppressed splicing inhibition of spectinomycin by 10% and 50 uM Co^2+ ion also suppressed splicing inhibition of specinomycin by 10%. Mg^2+ ion at 6 mM concentration decreased splicing inhibition of spectinomycin by 42% while Mn^2+ ion decreased the splicing inhibition by 10%. Zn^2+ ion at 10 uM concentration lowered the splicing inhibition by spectinomycin of 15%. Of all divalent cations tested, Mg^2+ ion was the most effective in suppressing splicing inhibition by specinomycin whereas Ca^2+ ion was the least effective. The results suggest that spectinomycin may interact with specific and functional Mg^2+ -binding sites within intron RNA that lead to a displacement of Mg^2+ essential for catalytic activity.

• Keywords: Spectinomycin; divalent cations; T4 phage; td intron RNA