Binding of methylmercuric hydroxide by 4-thiouridine of N-formylmethionyl-tRNA from Escherichia coli.

The binding of methylmercuric hydroxide to N-formylmethionyl-tRNA of Escherichia coli has been studied. In the absence of magnesium ions, methylmercury binds strongly to 4-thiouridine in the eighth position from the 5' end: the dissociation constant is (1.0 +/- 0.2) X 10(-5) M, and the forward and reverse rate constants for binding are (5.3 +/- 0.5) X 10(4) M-1S-1 and 0.38 +/- 0.02S-1, respectively. The presence of Mg2+ prevents this binding, presumably through some conformational change induced in the structure of N-formylmethionyl-tRNA.