[Selective binding of tRNA by RNA dependent DNA-polymerase from Escherichia coli].

Highly purified RNA dependent DNA-polymerase was isolated recently from E. coli by Romashchenko et al. [8]. The present data demonstrate that total E. coli tRNA inhibits poly(dT) synthesis on poly (A): oligo (dT) catalyzed by the enzyme when the enzyme:tRNA ratio is about 1 : 80--100. The inhibition results from the binding of certain tRNA's by the enzyme. The enzyme tRNA complex was separated from the unbound tRNA's by gel-filtration of Sephadex G-100. The tRNA's extracted from the complex are able to inhibit completely poly(A):oligo(dT) templated synthesis of poly(dT) under the enzyme:tRNA ratio about 1 : 2--3. Aminoacylation of tRNA separated from the enzyme complex has shown that E. coli RNA dependent DNA-polymerase selectively binds tRNAThr and to a lesser extent tRNATyr and tRNALys. It is suggested that the enzyme bound tRNA's carry out the functions of natural primers which compete with oligo(dT) for the enzyme responsible for the primer binding.