The chromatographic, catalytic and DNA-binding properties of yeast RNA polymerase III are highly affected by both concentration and type of salt. The type of anion is an especially important modulating factor for the enzymological properties of the enzyme. When acetate or sulfate anions are substituted for chloride anions, RNA polymerase III exhibits a higher affinity for DEAE-Sephadex A25, becomes able to transcribe DNA at relatively high ionic strength and shows a significant increase in the binding strength to DNA. A quantitative analysis of the binding of the enzyme to single-stranded DNA shows that the number of ionic contacts in the complex is not affected by the type of anion, but the nonionic contribution to the binding constant is significantly increased when acetate is substituted for chloride.
Anions Catalysis