Substrate specificity of Salmonella typhimurium RNAase III and the nature of products formed.

RNAase III, an endonuclease specific for double-stranded substrates, has been obtained in a highly purified form from extracts of Salmonella typhimurium. Poly (I-C) and a mixture of poly(A) and poly(U) (1 : 1), the latter in presence of 5 mM Mg2+, act as excellent substrates. Poly(I-C) is only partially hydrolysed by RNAase III and the product or products are acted upon by both RNAase I and RNAase II indicating that the products may be oligonucleotides. This conclusion is supported by two-dimensional chromatography on DEAE paper.